Air filtration arrangements having fluted media constructions and methods

ABSTRACT

Filter arrangements include a barrier media in the form of fluted media treated with a deposit of fine fibers. The media is particularly advantageous in high temperature (greater than 140 to 240° F.) systems. Such systems may include engine systems, gas turbine systems, and fuel cell systems. Filter arrangements may take the form of media packs having a circular cross-section or a racetrack shaped cross-section, or media packs formed in a panel configuration.

[0001] This application claims priority under 35 U.S.C. §119(e) to U.S.provisional application serial No. 60/230,138, filed on 5 Sep. 2000,incorporated by reference herein.

FIELD OF THE INVENTION

[0002] The invention relates to a filter arrangement and filtrationmethod. More specifically, it concerns an arrangement for filteringparticulate material from a gas flow stream, for example, an air stream.The invention also concerns a method for achieving the desirable removalof particulate material from such a gas flow stream.

[0003] The present invention is an on-going development of DonaldsonCompany Inc., of Minneapolis, Minn., the assignee of the presentinvention. The disclosure concerns continuing technology developmentrelated, in part, to the subjects characterized in U.S. Pat. Nos. B24,720,292; Des No. 416,308; 5,613,992; 4,020,783; and 5,112,372. Each ofthe patents identified in the previous sentence is also owned byDonaldson, Inc., of Minneapolis, Minn.; and, the complete disclosure ofeach is incorporated herein by reference.

[0004] The invention also relates to filters comprising a substratehaving a fine fiber layer made of polymer materials that can bemanufactured with improved environmental stability to heat, humidity,reactive materials and mechanical stress. Such materials can be used inthe formation of fine fibers such as microfibers and nanofiber materialswith improved stability and strength. As the size of fiber is reducedthe survivability of the materials is increasingly more of a problem.Such fine fibers are useful in a variety of applications. In oneapplication, filter structures can be prepared using this fine fibertechnology. The invention relates to polymers, polymeric composition,fiber, filters, filter constructions, and methods of filtering.Applications of the invention particularly concern filtering ofparticles from fluid streams, for example from air streams and liquid(e.g. non-aqueous and aqueous) streams. The techniques described concernstructures having one or more layers of fine fibers in the filter media.The compositions and fiber sizes are selected for a combination ofproperties and survivability.

BACKGROUND OF THE INVENTION

[0005] Gas streams often carry particulate material therein. In manyinstances, it is desirable to remove some or all of the particulatematerial from a gas flow stream. For example, air intake streams toengines for motorized vehicles or power generation equipment, gasstreams directed to gas turbines, and air streams to various combustionfurnaces, often include particulate material therein. The particulatematerial, should it reach the internal workings of the variousmechanisms involved, can cause substantial damage thereto. Removal ofthe particulate material from the gas flow upstream of the engine,turbine, furnace or other equipment involved is often needed.

[0006] The invention relates to polymeric compositions with improvedproperties that can be used in a variety of applications including theformation of fibers, microfibers, nanofibers, fiber webs, fibrous mats,permeable structures such as membranes, coatings or films. The polymericmaterials of the invention are compositions that have physicalproperties that permit the polymeric material, in a variety of physicalshapes or forms, to have resistance to the degradative effects ofhumidity, heat, air flow, chemicals and mechanical stress or impact.

[0007] In making fine fiber filter media, a variety of materials havebeen used including fiberglass, metal, ceramics and a range of polymericcompositions. A variety of fiber forming methods or techniques have beenused for the manufacture of small diameter micro- and nanofibers. Onemethod involves passing the material through a fine capillary or openingeither as a melted material or in a solution that is subsequentlyevaporated. Fibers can also be formed by using “spinnerets” typical forthe manufacture of synthetic fiber such as nylon. Electrostatic spinningis also known. Such techniques involve the use of a hypodermic needle,nozzle, capillary or movable emitter. These structures provide liquidsolutions of the polymer that are then attracted to a collection zone bya high voltage electrostatic field. As the materials are pulled from theemitter and accelerate through the electrostatic zone, the fiber becomesvery thin and can be formed in a fiber structure by solvent evaporation.

[0008] As more demanding applications are envisioned for filtrationmedia, significantly improved materials are required to withstand therigors of high temperature 100° F. to 250° F., often 140° F. to 240° F.and up to 300° F., high humidity 10% to 90% up to 100% RH, high flowrates of both gas and liquid, and filtering micron and submicronparticulates (ranging from about 0.01 to over 10 microns) and removingboth abrasive and non-abrasive and reactive and non-reactive particulatefrom the fluid stream.

[0009] Accordingly, a substantial need exists for polymeric materials,micro- and nanofiber materials and filter structures that provideimproved properties for filtering streams with higher temperatures,higher humidities, high flow rates and said micron and submicronparticulate materials.

[0010] A variety of air filter or gas filter arrangements have beendeveloped for particulate removal. However, in general, continuedimprovements are sought.

SUMMARY OF THE INVENTION

[0011] Herein, general techniques for the design and application of aircleaner arrangements are provided. The techniques include preferredfilter element design, as well as the preferred methods of applicationand filtering.

[0012] In general, the preferred applications concern utilization,within an air filter, of Z-shaped media, including a composite of asubstrate and fine fibers, to advantage.

[0013] The filter media includes at least a micro- or nanofiber weblayer in combination with a substrate material in a mechanically stablefilter structure. These layers together provide excellent filtering,high particle capture, and efficiency at minimum flow restriction when afluid such as a gas or liquid passes through the filter media Thesubstrate can be positioned in the fluid stream upstream, downstream orin an internal layer. The fiber can be positioned on the upstream, thedown stream or both sides of a filter substrate, regardless of filtergeometry. The fiber is generally placed on the upstream side. However iscertain applications downstream placement can be useful. In certainapplications, double sided structure is useful. A variety of industrieshave directed substantial attention in recent years to the use offiltration media for filtration, i.e. the removal of unwanted particlesfrom a fluid such as gas or liquid. The common filtration processremoves particulate from fluids including an air stream or other gaseousstream or from a liquid stream such as a hydraulic fluid, lubricant oil,fuel, water stream or other fluids. Such filtration processes requirethe mechanical strength, chemical and physical stability of themicrofiber and the substrate materials. The filter media can be exposedto a broad range of temperature conditions, humidity, mechanicalvibration and shock and both reactive and non-reactive, abrasive ornon-abrasive particulates entrained in the fluid flow. When in normaloperation, the filter is generally exposed to air at or near ambientconditions or at slightly elevated temperature. The filter can beexposed to higher temperature when the engine is operated abnormally orwhen the engine is shut down after extended service. If the engine isnot in operation, air does not pass through the filter. The filterrapidly reaches under hood temperature. Further, the filtration mediaoften require the self-cleaning ability of exposing the filter media toa reverse pressure pulse (a short reversal of fluid flow to removesurface coating of particulate) or other cleaning mechanism that canremove entrained particulate from the surface of the filter media. Suchreverse cleaning can result in substantially improved (i.e.) reducedpressure drop after the pulse cleaning. Particle capture efficiencytypically is not improved after pulse cleaning, however pulse cleaningwill reduce pressure drop, saving energy for filtration operation. Suchfilters can be removed for service and cleaned in aqueous or non-aqueouscleaning compositions. Such media are often manufactured by spinningfine fiber and then forming an interlocking web of microfiber on aporous substrate. In the spinning process the fiber can form physicalbonds between fibers to interlock the fiber mat into a integrated layer.Such a material can then be fabricated into the desired filter formatsuch as cartridges, flat disks, canisters, panels, bags and pouches.Within such structures, the media can be substantially pleated, rolledor otherwise positioned on support structures.

[0014] The filter arrangements described herein can be utilized in awide variety of applications including, for example, dust collection,air compressors, on-road and off-road engines, gas turbine systems,power generators such as fuel cells and others.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 depicts a typical electrostatic emitter driven apparatusfor production of the fine fibers of the invention.

[0016]FIG. 2 shows the apparatus used to introduce fine fiber ontofilter substrate into the fine fiber forming technology shown in FIG. 1.

[0017]FIG. 3 is a depiction of the typical internal structure of asupport material and a separate depiction of the fine fiber material ofthe invention compared to small, i.e. 2 and 5 micron particulatematerials.

[0018]FIGS. 4 through 11 are analytical ESCA spectra relating to Example13.

[0019]FIG. 12 shows the stability of the 0.23 and 0.45 microfibermaterial of the invention from Example 5.

[0020]FIGS. 13 through 16 show the improved temperature and humiditystability of the materials of Examples 5 and 6 when compared tounmodified nylon copolymer solvent soluble polyamide.

[0021]FIGS. 17 through 20 demonstrate that the blend of two copolymers,a nylon homopolymer and a nylon copolymer, once heat treated andcombined with additives form a single component material that does notdisplay distinguishable characteristics of two separate polymermaterials, but appears to be a crosslinked or otherwise chemicallyjoined single phase.

[0022]FIG. 21 is a schematic view of an engine system in which aircleaners according to the present disclose may be utilized;

[0023]FIG. 22 is a schematic, perspective view of one embodiment of afilter element that may be utilized in the system depicted in FIG. 21;

[0024]FIG. 23 is a schematic, perspective view of a portion of filtermedia (Z-media) useable in the arrangement of FIG. 22;

[0025]FIG. 24 is a schematic, cross-sectional view of the filter elementdepicted in FIG. 22 insalled within a housing;

[0026]FIG. 25 is a fragmented, enlarged, schematic view of oneembodiment of a compressible seal member utilized in a sealing systemfor the filter element of FIG. 22;

[0027]FIG. 26 is a schematic, perspective view of another embodiment ofa filter element that may be utilized in the engine system of FIG. 21;

[0028]FIG. 27 is a schematic, cross-sectional view of the filter elementof FIG. 26 installed within a housing;

[0029]FIG. 28 is a schematic, exploded, perspective view of anotherembodiment of a filter element and housing that may be utilized in theengine system of FIG. 21;

[0030]FIG. 29 is a schematic depiction of a gas turbine system in whichfilter elements according to the present disclosure may be utilized;

[0031]FIG. 30 is a schematic, perspective view of one embodiment of afilter element that may be useable in gas turbine air intake systemsdepicted in FIG. 29;

[0032]FIG. 31 is a rear elevational view of the filter element depictedin FIG. 30 installed within a tube sheet, and having a prefilterinstalled upstream of the filter element of FIG. 30;

[0033]FIG. 32 is an enlarged, schematic, fragmented, cross-sectionalview of the air filter arrangement of FIG. 31, taken along the line12-12 of FIG. 31;

[0034]FIG. 33 is a schematic view of an air intake system for amicroturbine system, in which filter elements of the present disclosuremay be utilized;

[0035]FIG. 34 is a schematic, cross-sectional view of a filter elementin an operable installation to clean intake air in a gas turbine system,the cross-section being taken along the line 14-14 of FIG. 35, but in anassembled state;

[0036]FIG. 35 is an exploded, side elevational view of the filterarrangement of FIG. 34, and in an unassembled state;

[0037]FIG. 36 is a fragmented, schematic, cross-sectional view showingthe filter element sealed within a filter housing;

[0038]FIG. 37 is a schematic view of an air intake for a fuel cellsystem, which may utilize filter elements disclosed herein;

[0039]FIG. 38 is a schematic, cross-sectional view of a filter assemblythat may be utilized in the fuel cell air intake system of FIG. 37; and

[0040]FIG. 39 is a schematic, cross-sectional view of another embodimentof a filter assembly that may be utilized in the air intake for a fuelcell system.

DETAILED DESCRIPTION OF THE INVENTION A. Micro Fiber or Fine FiberPolymer Materials

[0041] The invention provides an improved polymeric material. Thispolymer has improved physical and chemical stability. The polymer finefiber (microfiber and nanofiber) can be fashioned into useful productformats. The fiber can have a diameter of about 0.001 to 10 microns,about 0.005 to 5 microns, about 0.01 to 0.5 micron. Nanofiber is a fiberwith diameter less than 200 nanometer or 0.2 micron. Microfiber is afiber with diameter larger than 0.2 micron, but not larger than 10microns.

[0042] This fine fiber can be made in the form of an improvedmulti-layer microfiltration media structure. The fine fiber layers ofthe invention comprise a random distribution of fine fibers which can bebonded to form an interlocking net. Filtration performance is obtainedlargely as a result of the fine fiber barrier to the passage ofparticulate. Structural properties of stiffness, strength, pleatabilityare provided by the substrate to which the fine fiber adhered. The finefiber interlocking networks have as important characteristics, finefibers in the form of microfibers or nanofibers and relatively smallspaces between the fibers. Such interfiber spaces in the layer typicallyrange, between fibers, of about 0.01 to about 25 microns or often about0.1 to about 10 microns. The filter products comprise a fine fiber,layer on a choice of appropriate substrate such as a synthetic layer, anatural layer or a mixed natural/synthetic substrate. The fine fiberadds less than 5 microns, often less than 3 microns of thickness. Thefine fiber in certain applications adds about 1 to 10 or 1 to 5 finefiber diameters in thickness to the overall fine fiber plus substratefilter media In service, the filters can stop incident particulate frompassing to the substrate or through the fine fiber layer and can attainsubstantial surface loadings of trapped particles. The particlescomprising dust or other incident particulates rapidly form a dust cakeon the fine fiber surface and maintains high initial and overallefficiency of particulate removal. Even with relatively finecontaminants having a particle size of about 0.01 to about 1 micron, thefilter media comprising the fine fiber has a very high dust capacity.

[0043] The polymer materials as disclosed herein have substantiallyimproved resistance to the undesirable effects of heat, humidity, highflow rates, reverse pulse cleaning, operational abrasion, submicronparticulates, cleaning of filters in use and other demanding conditions.The improved microfiber and nanofiber performance is a result of theimproved character of the polymeric materials forming the microfiber ornanofiber. Further, the filter media of the invention using the improvedpolymeric materials of the invention provides a number of advantageousfeatures including higher efficiency, lower flow restriction, highdurability (stress related or environmentally related) in the presenceof abrasive particulates and a smooth outer surface free of loose fibersor fibrils. The overall structure of the filter materials provides anoverall thinner media allowing improved media area per unit volume,reduced velocity through the media, improved media efficiency andreduced flow restrictions.

[0044] The polymer can be an additive polymer, a condensation polymer ormixtures or blends thereof. A preferred mode of the invention is apolymer blend comprising a first polymer and a second, but differentpolymer (differing in polymer type, molecular weight or physicalproperty) that is conditioned or treated at elevated temperature. Thepolymer blend can be reacted and formed into a single chemical specie orcan be physically combined into a blended composition by an annealingprocess. Annealing implies a physical change, like crystallinity, stressrelaxation or orientation. Preferred materials are chemically reactedinto a single polymeric specie such that a Differential ScanningCalorimeter analysis reveals a single polymeric material. Such amaterial, when combined with a preferred additive material, can form asurface coating of the additive on the microfiber that providesoleophobicity, hydrophobicity or other associated improved stabilitywhen contacted with high temperature, high humidity and difficultoperating conditions. The fine fiber of the class of materials can havea diameter of 0.001 micron to 10 microns. Useful sizes include 0.001 to2 microns, 0.005 to 5 microns, 0.01 to 5 microns, depending on bonding,substrate and application. Such microfibers can have a smooth surfacecomprising a discrete layer of the additive material or an outer coatingof the additive material that is partly solubilized or alloyed in thepolymer surface, or both. Preferred materials for use in the blendedpolymeric systems include nylon 6; nylon 66; nylon 6-10; nylon(6-66-610) copolymers and other linear generally aliphatic nyloncompositions. A preferred nylon copolymer resin (SVP-651) was analyzedfor molecular weight by the end group titration. (J. E. Walz and G. B.Taylor, determination of the molecular weight of nylon, Anal. Chem. Vol.19, Number 7, pp 448-450 (1947). A number average molecular weight (Mn)was between 21,500 and 24,800. The composition was estimated by thephase diagram of melt temperature of three component nylon, nylon 6about 45%, nylon 66 about 20% and nylon 610 about 25%. (Page 286, NylonPlastics Handbook, Melvin Kohan ed. Hanser Publisher, New York (1995)).

[0045] Reported physical properties of SVP 651 resin are: Property ASTMMethod Units Typical Value Specific Gravity D-792 —   1.08 WaterAbsorption D-570 %   2.5 (24 hr immersion) Hardness D-240 Shore D 65 Melting Point DSC ° C.(° F.) 154 (309) Tensile Strength D-638 MPa (kpsi) 50 (7.3) @ Yield Elongation at Break D-638 % 350  Flexural ModulusD-790 MPa (kpsi) 180 (26) Volume Resistivity D-257 ohm-cm 10¹²

[0046] A polyvinylalcohol having a hydrolysis degree of from 87 to99.9+% can be used in such polymer systems. These are preferably crosslinked. And they are most preferably crosslinked and combined withsubstantial quantities of the oleophobic and hydrophobic additivematerials.

[0047] Another preferred mode of the invention involves a singlepolymeric material combined with an additive composition to improvefiber lifetime or operational properties. The preferred polymers usefulin this aspect of the invention include nylon polymers, polyvinylidenechloride polymers, polyvinylidene fluoride polymers, polyvinylalcoholpolymers and, in particular, those listed materials when combined withstrongly oleophobic and hydrophobic additives that can result in amicrofiber or nanofiber with the additive materials formed in a coatingon the fine fiber surface. Again, blends of similar polymers such as ablend of similar nylons, similar polyvinylchloride polymers, blends ofpolyvinylidene chloride polymers are useful in this invention. Further,polymeric blends or alloys of differing polymers are also contemplatedby the invention. In this regard, compatible mixtures of polymers areuseful in forming the microfiber materials of the invention. Additivecomposition such a fluoro-surfactant, a nonionic surfactant, lowmolecular weight resins (e.g.) tertiary butylphenol resin having amolecular weight of less than about 3000 can be used. The resin ischaracterized by oligomeric bonding between phenol nuclei in the absenceof methylene bridging groups. The positions of the hydroxyl and thetertiary butyl group can be randomly positioned around the rings.Bonding between phenolic nuclei always occurs next to hydroxyl group,not randomly. Similarly, the polymeric material can be combined with analcohol soluble non-linear polymerized resin formed from bis-phenol A.Such material is similar to the tertiary butylphenol resin describedabove in that it is formed using oligomeric bonds that directly connectaromatic ring to aromatic ring in the absence of any bridging groupssuch as alkylene or methylene groups.

[0048] Preferred polymer systems of the invention have adheringcharacteristic such that when contacted with a cellulosic substrateadheres to the substrate with sufficient strength such that it issecurely bonded to the substrate and can resist the delaminating effectsof a reverse pulse cleaning technique and other mechanical stresses. Insuch a mode, the polymer material must stay attached to the substratewhile undergoing a pulse clean input that is substantially equal to thetypical filtration conditions except in a reverse direction across thefilter structure. Such adhesion can arise from solvent effects of fiberformation as the fiber is contacted with the substrate or the posttreatment of the fiber on the substrate with heat or pressure. However,polymer characteristics appear to play an important role in determiningadhesion, such as specific chemical interactions like hydrogen bonding,contact between polymer and substrate occurring above or below Tg, andthe polymer formulation including additives. Polymers plasticized withsolvent or steam at the time of adhesion can have increased adhesion.

[0049] An important aspect of the invention is the utility of suchmicrofiber or nanofiber materials formed into a filter structure. Insuch a structure, the fine fiber materials of the invention are formedon and adhered to a filter substrate. Natural fiber and synthetic fibersubstrates, like spun bonded fabrics, non-woven fabrics of syntheticfiber and non-wovens made from the blends of cellulosics, synthetic andglass fibers, non-woven and woven glass fabrics, plastic screen likematerials both extruded and hole punched, UF and MF membranes of organicpolymers can be used. Sheet-like substrate or cellulosic non-woven webcan then be formed into a filter structure that is placed in a fluidstream including an air stream or liquid stream for the purpose ofremoving suspended or entrained particulate from that stream. The shapeand structure of the filter material is up to the design engineer. Oneimportant parameter of the filter elements after formation is itsresistance to the effects of heat, humidity or both. One aspect of thefilter media of the invention is a test of the ability of the filtermedia to survive immersion in warm water for a significant period oftime. The immersion test can provide valuable information regarding theability of the fine fiber to survive hot humid conditions and to survivethe cleaning of the filter element in aqueous solutions that can containsubstantial proportions of strong cleaning surfactants and strongalkalinity materials. Preferably, the fine fiber materials of theinvention can survive immersion in hot water while retaining at least30%, preferably 50% of the fine fiber formed on the surface of thesubstrate. Retention of at least 30%, preferably 50% of the fine fibercan maintain substantial fiber efficiency without loss of filtrationcapacity or increased back pressure. Most preferably retaining at least75%. The thickness of the typical fine fiber filtration layer rangesfrom about 1 to 100 times the fiber diameter with a basis weight rangingfrom about 0.01 to 240 micrograms-cm⁻².

[0050] Fluid streams such as air and gas streams often carry particulatematerial therein. The removal of some or all of the particulate materialfrom the fluid stream is needed. For example, air intake streams to thecabins of motorized vehicles, air in computer disk drives, HVAC air,aircraft cabin ventilation, clean room ventilation and applicationsusing filter bags, barrier fabrics, woven materials, air to engines formotorized vehicles, or to power generation equipment; gas streamsdirected to gas turbines; and, air streams to various combustionfurnaces, often include particulate material therein. In the case ofcabin air filters it is desirable to remove the particulate matter forcomfort of the passengers and/or for aesthetics. With respect to air andgas intake streams to engines, gas turbines and combustion firnaces, itis desirable to remove the particulate material because particulate cancause substantial damage to the internal workings to the variousmechanisms involved. In other instances, production gases or off gasesfrom industrial processes or engines may contain particulate materialtherein. Before such gases can be, or should be, discharged throughvarious downstream equipment to the atmosphere, it may be desirable toobtain a substantial removal of particulate material from those streams.

[0051] A general understanding of some of the basic principles andproblems of air filter design can be understood by consideration of thefollowing types of filter media: surface loading media; and, depthmedia. Each of these types of media has been well studied, and each hasbeen widely utilized. Certain principles relating to them are described,for example, in U.S. Pat. Nos. 5,082,476; 5,238,474; and 5,364,456. Thecomplete disclosures of these three patents are incorporated herein byreference.

[0052] The “lifetime” of a filter is typically defined according to aselected limiting pressure drop across the filter. The pressure buildupacross the filter defines the lifetime at a defined level for thatapplication or design. Since this buildup of pressure is a result ofload, for systems of equal efficiency a longer life is typicallydirectly associated with higher capacity. Efficiency is the propensityof the media to trap, rather than pass, particulates. It should beapparent that typically the more efficient a filter media is at removingparticulates from a gas flow stream in general the more rapidly thefilter media will approach the “lifetime” pressure differential(assuming other variables to be held constant).

DETAILED DESCRIPTION OF CERTAIN DRAWINGS

[0053] The microfiber or nanofiber of the unit can be formed by theelectrostatic spinning process. A suitable apparatus for forming thefiber is illustrated in FIG. 1. This apparatus includes a reservoir 80in which the fine fiber forming polymer solution is contained, a pump 81and a rotary type emitting device or emitter 40 to which the polymericsolution is pumped. The emitter 40 generally consists of a rotatingunion 41, a rotating portion 42 including a plurality of offset holes 44and a shaft 43 connecting the forward facing portion and the rotatingunion. The rotating union 41 provides for introduction of the polymersolution to the forward facing portion 42 through the hollow shaft 43.The holes 44 are spaced around the periphery of the forward facingportion 42. Alternatively, the rotating portion 42 can be immersed intoa reservoir of polymer fed by reservoir 80 and pump 81. The rotatingportion 42 then obtains polymer solution from the reservoir and as itrotates in the electrostatic field, a droplet of the solution isaccelerated by the electrostatic field toward the collecting media 70 asdiscussed below.

[0054] Facing the emitter 40, but spaced apart therefrom, is asubstantially planar grid 60 upon which the collecting media 70 (i.e.substrate or combined substrate is positioned. Air can be drawn throughthe grid. The collecting media 70 is passed around rollers 71 and 72which are positioned adjacent opposite ends of grid 60. A high voltageelectrostatic potential is maintained between emitter 40 and grid 60 bymeans of a suitable electrostatic voltage source 61 and connections 62and 63 which connect respectively to the grid 60 and emitter 40.

[0055] In use, the polymer solution is pumped to the rotating union 41or reservoir from reservoir 80. The forward facing portion 42 rotateswhile liquid exits from holes 44, or is picked up from a reservoir, andmoves from the outer edge of the emitter toward collecting media 70positioned on grid 60. Specifically, the electrostatic potential betweengrid 60 and the emitter 40 imparts a charge to the material which causeliquid to be emitted therefrom as thin fibers which are drawn towardgrid 60 where they arrive and are collected on substrate 12 or anefficiency layer 14. In the case of the polymer in solution, solvent isevaporated off the fibers during their flight to the grid 60; therefore,the fibers arrive at the substrate 12 or efficiency layer 14. The finefibers bond to the substrate fibers first encountered at the grid 60.Electrostatic field strength is selected to ensure that the polymermaterial as it is accelerated from the emitter to the collecting media70, the acceleration is sufficient to render the material into a verythin microfiber or nanofiber structure. Increasing or slowing theadvance rate of the collecting media can deposit more or less emittedfibers on the forming media, thereby allowing control of the thicknessof each layer deposited thereon. The rotating portion 42 can have avariety of beneficial positions. The rotating portion 42 can be placedin a plane of rotation such that the plane is perpendicular to thesurface of the collecting media 70 or positioned at any arbitrary angle.The rotating media can be positioned parallel to or slightly offset fromparallel orientation.

[0056]FIG. 2 is a general schematic diagram of a process and apparatusfor forming a layer of fine fiber on a sheet-like substrate or media. InFIG. 2, the sheet-like substrate is unwound at station 20. Thesheet-like substrate 20 a is then directed to a splicing station 21wherein multiple lengths of the substrate can be spliced for continuousoperation. The continuous length of sheet-like substrate is directed toa fine fiber technology station 22 comprising the spinning technology ofFIG. 1 wherein a spinning device forms the fine fiber and lays the finefiber in a filtering layer on the sheet-like substrate. After the finefiber layer is formed on the sheet-like substrate in the formation zone22, the fine fiber layer and substrate are directed to a heat treatmentstation 23 for appropriate processing. The sheet-like substrate and finefiber layer is then tested in an efficiency monitor 24 and nipped ifnecessary at a nip station 25. The sheet-like substrate and fiber layeris then steered to the appropriate winding station to be wound onto theappropriate spindle for further processing 26 and 27.

[0057]FIG. 3 is a scanning electromicrograph image showing therelationship of typical dust particles having a diameter of about 2 andabout 5 microns with respect to the sizes of pores in typical cellulosemedia and in the typical fine fiber structures. In FIG. 3a, the 2 micronparticle 31 and the 5 micron particle 32 is shown in a cellulosic media33 with pore sizes that are shown to be quite a bit larger than thetypical particle diameters. In sharp contrast, in FIG. 3B, the 2 micronparticle 31 appears to be approximately equal to or greater than thetypical openings between the fibers in the fiber web 35 while the 5micron particle 32 appears to be larger than any of the openings in thefine fiber web 35.

[0058] The foregoing general description of the various aspects of thepolymeric materials of the invention, the fine fiber materials of theinvention including both microfibers and nanofibers and the constructionof useful filter structures from the fine fiber materials of theinvention provides an understanding of the general technologicalprinciples of the operation of the invention. The following specificexemplary materials are examples of materials that can be used in theformation of the fine fiber materials of the invention and the followingmaterials disclose a best mode. The following exemplary materials weremanufactured with the following characteristics and process conditionsin mind. Electrospinning small diameter fiber less than 10 micron isobtained using an electrostatic force from a strong electric fieldacting as a pulling force to stretch a polymer jet into a very finefilament. A polymer melt can be used in the electrospinning process,however, fibers smaller than 1 micron are best made from polymersolution. As the polymer mass is drawn down to smaller diameter, solventevaporates and contributes to the reduction of fiber size. Choice ofsolvent is critical for several reasons. If solvent dries too quickly,then fibers tends to be flat and large in diameter. If the solvent driestoo slowly, solvent will redissolve the formed fibers. Thereforematching drying rate and fiber formation is critical. At high productionrates, large quantities of exhaust air flow helps to prevent a flammableatmosphere, and to reduce the risk of fire. A solvent that is notcombustible is helpful. In a production environment the processingequipment will require occasional cleaning. Safe low toxicity solventsminimize worker exposure to hazardous chemicals. Electrostatic spinningcan be done at a flow rate of 1.5 ml/min per emitter, a target distanceof 8 inches, an emitter voltage of 88 kV, an emitter rpm of 200 and arelative humidity of 45%.

[0059] The choice of polymer system is important for a givenapplication. For pulse cleaning application, an extremely thin layer ofmicrofiber can help to minimize pressure loss and provide an outersurface for particle capture and release. A thin layer of fibers of lessthan 2-micron diameter, preferably less than 0.3-micron diameter ispreferred. Good adhesion between microfiber or nanofiber and substratesupon which the microfibers or nanofibers are deposited is important.When filters are made of composites of substrate and thin layer ofmicro- and nanofibers, such composite makes an excellent filter mediumfor self-cleaning application. Cleaning the surface by back pulsingrepeatedly rejuvenates the filter medium. As a great force is exerted onthe surface, fine fiber with poor adhesion to substrates can delaminateupon a back pulse that passes from the interior of a filter through asubstrate to the micro fiber. Therefore, good cohesion between microfibers and adhesion between substrate fibers and electrospun fibers iscritical for successful use.

[0060] Products that meet the above requirements can be obtained usingfibers made from different polymer materials. Small fibers with goodadhesion properties can be made from such polymers like polyvinylidenechloride, poly vinyl alcohol and polymers and copolymers comprisingvarious nylons such as nylon 6, nylon 4,6; nylon 6,6; nylon 6,10 andcopolymers thereof. Excellent fibers can be made from PVDF, but to makesufficiently small fiber diameters requires chlorinated solvents. Nylon6, Nylon 66 and Nylon 6,10 can be electrospun. But, solvents such asformic acid, m-cresol, tri-fluoro ethanol, hexafluoro isopropanol areeither difficult to handle or very expensive. Preferred solvents includewater, ethanol, isopropanol, acetone and N-methyl pyrrolidone due totheir low toxicity. Polymers compatible with such solvent systems havebeen extensively evaluated. We have found that fibers made from PVC,PVDC, polystyrene, polyacrylonitrile, PMMA, PVDF require additionaladhesion means to attain structural properties. We also found that whenpolymers are dissolved in water, ethanol, isopropanol, acetone, methanoland mixtures thereof and successfully made into fibers, they haveexcellent adhesion to the substrate, thereby making an excellent filtermedium for self-cleaning application. Self-cleaning via back air pulseor twist is useful when filer medium is used for very high dustconcentration. Fibers from alcohol soluble polyamides and poly(vinylalcohol)s have been used successfully in such applications. Examples ofalcohol soluble polyamides include Macromelt 6238, 6239, and 6900 fromHenkel, Elvamide 8061 and 8063 from dupont and SVP 637 and 651 fromShakespeare Monofilament Company. Another group of alcohol solublepolyamide is type 8 nylon, alkoxy alkyl modifies nylon 66 (Ref. Page447, Nylon Plastics handbook, Melvin Kohan ed. Hanser Publisher, NewYork, 1995). Examples of poly(vinyl alcohol) include PVA-217, 224 fromKuraray, Japan and Vinol 540 from Air Products and Chemical Company.

[0061] We have found that filters can be exposed to extremes inenvironmental conditions. Filters in Saudi Arabian desert can be exposedto temperature as high as 150 F° or higher. Filters installed inIndonesia or Gulf Coast of US can be exposed high humidity above 90% RHand high temperature of 100 F°. Or, they can be exposed to rain. We havefound that filters used under the hood of mobile equipment like cars,trucks, buses, tractors, and construction equipment can be exposed tohigh temperature (+200° F.), high relative humidity and other chemicalenvironment. We have developed test methods to evaluate survivability ofmicrofiber systems under harsh conditions. Soaking the filter mediasamples in hot water (140 F°) for 5 minutes or exposure to highhumidity, high temperature and air flow.

B. General Principles Relating to Air Cleaner Design

[0062] Herein, the term “air cleaner” will be used in reference to asystem which functions to remove particulate material from an air flowstream. The term “air filter” references a system in which removal isconducted by passage of the air, carrying particulate therein, throughfilter media. The term “filter media” or “media” refers to a material orcollection of material through which the air passes, with a concomitantdeposition of the particles in or on the media. The term “surfaceloading media” or “barrier media” refers to a system in which as the airpasses through the media, the particulate material is primarilydeposited on the surface of the media, forming a filter cake, as opposedto into or through the depth of the media.

[0063] Herein the term “filter element” is generally meant to refer to aportion of the air cleaner which includes the filter media therein. Ingeneral, a filter element will be designed as a removable andreplaceable, i.e. serviceable, portion of the air cleaner. That is, thefilter media will be carried by the filter element and be separable fromthe remainder portion of the air cleaner so that periodically the aircleaner can be rejuvenated by removing a loaded or partially loadedfilter element and replacing it with a new, or cleaned, filter element.Preferably, the air cleaner is designed so that the removal andreplacement can be conducted by hand. By the term “loaded” or variantsthereof in this context, reference is meant to an air cleaner which hasbeen on-line a sufficient period of time to contain a significant amountof trapped particles or particulates thereon. In many instances, duringnormal operation, a filter element will increase in weight, due toparticulate loading therein, of two or three times (or more) itsoriginal weight.

[0064] In general, specifications for the performance of an air cleanersystem are, generated by the preferences of the original equipmentmanufacturer (OEM) for the engine involved and/or the OEM of the truckor other equipment involved. While a wide variety of specifications maybe involved, some of the major ones are the following:

[0065] 1. Engine air intake need (rated flow)

[0066] 2. Initial Restriction

[0067] 3. Initial efficiency

[0068] 4. Average or overall operating restriction

[0069] 5. Overall efficiency

[0070] 6. Filter service life

[0071] The engine air intake need is a function of the engine size, i.e.displacement and rpm at maximum, full or “rated” load. In general, it isthe product of displacement and rated rpm, modified by the volumetricefficiency, a factor which reflects turbo efficiency, duct efficiency,etc. In general, it is a measurement of the volume of air, per unittime, required by the engine or other system involved, during ratedoperation or fill load. While air intake need will vary depending uponrpm, the air intake requirement is defined at a rated rpm, often at 1800rpm or 2100 rpm for many typical truck engines. Herein this will becharacterized as the “rated air flow” or by similar terms. In general,principles characterized herein can be applied to air cleanerarrangements used with systems specified for operation over a wide rangeof ratings or demands, including, for example, ones in the range ofabout 3 cubic feet/min. (cefm) up to 10,000 cfin often 50 to 500 cfm.Such equipment includes, for example: small utility engines(motorcycles, lawn mowers, etc.), automotive engines, pickup trucks andsport utility vehicle engines, engines for small trucks and deliveryvehicles, buses, over-the-highway trucks, agricultural equipment (forexample tractors), construction equipment, mining equipment, marineengines, a variety of generator engines, and, in some instances, gasturbines and air compressors.

[0072] Air cleaner overall efficiency is generally a reflection of theamount of “filterable” solids which pass into the air cleaner duringuse, and which are retained by the air cleaner. It is typicallyrepresented as the percentage of solids passing into the air cleanerwhich are retained by the air cleaner in normal use, on a weight basis.It is evaluated and reported for many systems by using SAE standards,which techniques are generally characterized in U.S. Pat. No. 5,423,892at Column 25, line 60-Column 26, line 59; Column 27, lines 140. Atypical standard used is SAE J726, incorporated herein by reference.

[0073] With respect to efficiency, engine manufacturer and/or equipmentmanufacturer specifications will vary, in many instances, withefficiency demands (based on either SAE J726 or field testing) foroverall operation often being set at 99.5% or higher, typically at 99.8%or higher. With typical vehicle engines having air flow demands of 500cfm or above, specifications of 99.8% overall average, or higher, arenot uncommon.

[0074] Initial efficiency is the measurable efficiency of the filterwhen it is first put on line. As explained in U.S. Pat. No. 5,423,892 atColumn 27, lines 140, especially with conventional pleated paper(barrier type or surface-loading) filters, initial efficiency isgenerally substantially lower than the overall average efficiency duringuse. This is because the “dust cake” or contaminant build-up on thesurface of such a filter during operation, increases the efficiency ofthe filter. Initial efficiency is also often specified by the enginemanufacturer and/or the vehicle manufacturer. With typical vehicleengines having air flow demands of 500 cfm or above, specifications of98% or above (typically 98.5% or above) are common.

[0075] Restriction is the pressure differential across an air cleaner orair cleaner system during operation. Contributors to the restrictioninclude: the filter media through which the air is directed; duct sizethrough which the air is directed; and, structural features againstwhich or around which the air is directed as it flows through the aircleaner and into the engine. With respect to air cleaners, initialrestriction limits are often part of the specifications and demands ofthe engine manufacturer and/or equipment manufacturer. This initialrestriction would be the pressure differential measured across the aircleaner when the system is put on line with a clean air filter thereinand before significant loading occurs. Typically, the specifications forany given system have a maximum initial restriction requirement.

[0076] In general, engine and equipment manufacturers design equipmentwith specifications for air cleaner efficiency up to a maximumrestriction. As reported in U.S. Pat. No. 5,423,892, at Column 2, lines19-29; and, column 6, line 47, column 7, line 3, the limitingrestriction: for typical truck engines is a pressure drop of about 20-30inches of water, often about 25 inches of water; for automotive internalcombustion engines is about 20-25 inches of water; for gas turbines, istypically about 5 inches of water; and, for industrial ventilationsystems, is typically about 3 inches of water.

[0077] In general, some of the principal variables of concern in aircleaner design in order to develop systems to meet the types ofspecifications characterized in the previous section, are the following:

[0078] 1. filter media type, geometry and efficiency;

[0079] 2. air cleaner shape and structure; and

[0080] 3. filter element size.

[0081] For example, conventional cellulose fiber media or similar mediais generally a “barrier” filter. An example is paper media. In general,the operation of such media is through surface loading, i.e., when airis directed through the media, the surface of the media acts as abarrier or sieve, preventing passage of particulate materialtherethrough. In time, a dust cake builds on the surface of the media,increasing media efficiency. In general, the “tightness” or “porosity”of the fiber construction determines the efficiency, especially theinitial efficiency, of the system. In time, the filter cake will effect(increase) the efficiency.

[0082] In general, such media is often defined or specified by itspermeability. The permeability test for media is generally characterizedin U.S. Pat. No. 5,672,399 at Col. 19, lines 27-39. In general, it isthe media face velocity (air) required to induce a 0.50 inch waterrestriction across a flat sheet of the referenced material, media orcomposite. Permeability, as used herein, is assessed by a Frazier PermTest, according to ASTM D737 incorporated herein by reference, forexample using a Frazier Perm Tester available from Frazier PrecisionInstrument Co., Inc., Gaithersburg, Md., or by some analogous test.

[0083] The permeability of cellulose fiber media used in many types ofengine filters for trucks having rated air flows of 50 cfm or moremanufactured by Donaldson Company, is media having a permeability ofless than about 15 fpm, typically around 13 fpm. In general, in theengine filtration market, for such equipment, a variety of barrier media(pleated media) having permeability values of less than about 25 fpm,and typically somewhere within the range of 10-25 fpm, have been widelyutilized by various element manufacturers.

[0084] With respect to efficiency, principles vary with respect to thetype of media involved. For example, cellulose fiber or similar barriermedia is generally varied, with respect to efficiency, by varyingoverall general porosity or permeability.

C. Typical System; Engine Air Intake

[0085] In FIG. 21, a schematic view of a system is shown generally at130. System 130 is one example type of system in which air cleanerarrangements and constructions described herein is usable. In FIG. 21,equipment 131, such as a vehicle, having an engine 132 with some definedrated air flow demand, for example, at least 370 cfin, is shownschematically. Equipment 131 may comprise a bus, an over the highwaytruck, an off-road vehicle, a tractor, or marine application such as apower boat. Engine 132 powers equipment 131, through use of an air, fuelmixture. In FIG. 21, air flow is shown drawn into engine 132 at anintake region 133. An optional turbo 134 is shown in phantom, asoptionally boosting the air intake into the engine 132. An air cleaner135 having a media pack 136 is upstream of the engine 132 and turbo 134.In general, in operation, air is drawn in at arrow 137 into the aircleaner 135 and through media pack 136. There, particles andcontaminants are removed from the air. The cleaned air flows at arrow137 into the intake 133. From there, the air flows into engine 132, topower vehicle 131.

[0086] In engine systems, during operation of the engine, thetemperature, under the hood, typically is at least 120° F., and often isin the range of 140° F.-220° F. or more depending on operatingconditions. The temperature may adversely affect the operatingefficiency of the filter element. Regulations on emissions can increasethe restriction on the engine exhaust, causing further increasedtemperatures. As explained below, constructing the filter media in theform of a composite of a barrier media and at least a single layer, andin some instances, multiple layers of “fine fiber” can improve theperformance (the operating efficiency, in particular) of the filterelement over prior art filter elements that are not constructed fromsuch media composites.

D. Example Air Cleaners

[0087] Attention is directed to FIG. 22. FIG. 22 is a perspective viewof a first embodiment of a media pack 140. The preferred media pack 140depicted includes filter media 142 and a sealing system 144. Inpreferred constructions, the filter media 142 is designed to removeparticulates from a fluid, such as air, passing through the filter media142, while the sealing system 144 is designed to seal the media pack 140against a sidewall of a housing or duct, as shown in FIG. 24.

[0088] This media pack 140 of FIGS. 22-25 is generally described in U.S.Pat. No. 6,190,432, which is incorporated by reference herein.

[0089] In certain preferred arrangements, the filter media 142 will beconfigured for straight-through flow. By “straight-through flow,” it ismeant that the filter media 142 is configured in a construction 146 witha first flow face 148 (corresponding to an inlet end, in the illustratedembodiment) and an opposite, second flow face 150 (corresponding to anoutlet end, in the illustrated embodiment), with fluid flow entering inone direction 152 through the first flow face 148 and exiting in thesame direction 154 from the second flow face 150. When used with aninline-flow housing, in general, the fluid will enter through the inletof the housing in one direction, enter the filter construction 146through the first flow face 148 in the same direction, exit the filterconstruction 146 in the same direction from the second flow face 150,and exit the housing through the housing outlet also in the samedirection.

[0090] In FIG. 22, the first flow face 148 and the second flow face 150are depicted as planar and as parallel. In other embodiments, the firstflow face 148 and the second flow face 150 can be non-planar, forexample, frusto-conical. Further, the first flow face 148 and secondflow face 150 need not be parallel to each other.

[0091] Generally, the filter construction 146 will be a woundconstruction. That is, the construction 146 will typically include alayer of filter media that is turned completely or repeatedly about acenter point Typically, the wound construction will be a coil, in that alayer of filter media will be rolled a series of turns around a centerpoint. In arrangements where a wound, coiled construction is used, thefilter construction 146 will be a roll of filter media, typicallypermeable fluted filter media.

[0092] Attention is now directed to FIG. 23. FIG. 23 is schematic,perspective view demonstrating the principles of operation of certainpreferred media usable in the filter constructions herein. In FIG. 23, afluted construction of Z-media is generally designated at 156.Preferably, the fluted construction 156 includes: a layer 157 ofcorrugations having a plurality of flutes 158 and a face sheet 160. TheFIG. 22 embodiment shows two sections of the face sheet 160, at 160A(depicted on top of the corrugated layer 157) and at 160B (depictedbelow the corrugated layer 157). Typically, the preferred mediaconstruction 162 used in arrangements described herein will include thecorrugated layer 157 secured to the bottom face sheet 160B. When usingthis media construction 162 in a rolled construction, it typically willbe wound around itself, such that the bottom face sheet 160B will coverthe top of the corrugated layer 157. The face sheet 160 covering the topof the corrugated layer is depicted as 160A. It should be understoodthat the face sheet 160A and 160B are the same sheet 160.

[0093] When using this type of media construction 162, the flutechambers 158 preferably form alternating peaks 164 and troughs 166. Thetroughs 166 and peaks 164 divide the flutes into an upper row and lowerrow. In the particular configuration shown in FIG. 23, the upper flutesform flute chambers 168 closed at the downstream end 178, while flutechambers 170 having their upstream end 181 closed form the lower row offlutes. The fluted chambers 170 are closed by a first end bead 172 thatfills a portion of the upstream end 181 of the flute between the flutingsheet 171 and the second facing sheet 160B. Similarly, a second end bead174 closes the downstream end 178 of alternating flutes 168.

[0094] When using media constructed in the form of media construction162, during use, unfiltered fluid, such as air, enters the flutechambers 168 as indicated by the shaded arrows 176. The flute chambers168 have their upstream ends 169 open. The unfiltered fluid flow is notpermitted to pass through the downstream ends 178 of the flute chambers168 because their downstream ends 178 are closed by the second end bead174. Therefore, the fluid is forced to proceed through the fluting sheet171 or face sheets 160. As the unfiltered fluid passes through thefluting sheet 171 or face sheets 160, the fluid is cleaned or filtered.The cleaned fluid is indicated by the unshaded arrow 180. The fluid thenpasses through the flute chambers 170 (which have their upstream ends181 closed) to flow through the open downstream end 184 out the flutedconstruction 156. With the configuration shown, the unfiltered fluid canflow through the fluted sheet 171, the upper facing sheet 160A, or lowerfacing sheet 160B, and into a flute chamber 170.

[0095] Typically, the media construction 162 will be prepared and thenwound to form a rolled construction 146 of filter media. When this typeof media is selected for use, the media construction 162 preparedincludes the sheet of corrugations 157 secured with the end bead 172 tothe bottom face sheet 160B (as shown in FIG. 23, but without the topface sheet 160A).

[0096] Attention is again directed to FIG. 22. In FIG. 22, the secondflow face 150 is shown schematically. There is a portion at 182 in whichthe flutes including the open ends 184 and closed ends 178 are depicted.It should be understood that this section 182 is representative of theentire flow face 50. For the sake of clarity and simplicity, the flutesare not depicted in the other remaining portions 183 of the flow face150. Top and bottom plan views, as well as side elevational views of amedia pack 140 usable in the systems and arrangements described hereinare depicted in copending and commonly assigned U.S. patent applicationSer. No. 29/101,193, filed Feb. 26, 1999, and entitled, “Filter ElementHaving Sealing System,” herein incorporated by reference.

[0097] Turning now to FIG. 24, the filter construction 146 is showninstalled in a housing 186 (which can be part of an air intake duct intoan engine or turbo of an air cleaner 179). In the arrangement shown, airflows into the housing 186 at 187, through the filter construction 146,and out of the housing 186 at 188. When media constructions such asfilter constructions 46 of the type shown are used in a duct or housing186, the sealing system 144 will be needed to ensure that air flowsthrough the media construction 146, rather than bypass it.

[0098] The particular sealing system 144 depicted includes a flameconstruction 190 and a seal member 192. When this type of sealing system144 is used, the flame construction 190 provides a support structure orbacking against which the seal member 192 can be compressed against toform a radial seal 194 with the duct or housing 186.

[0099] Still in reference to FIG. 24, in the particular embodimentshown, the frame construction 190 includes a rigid projection 196 thatprojects or extends from at least a portion of one of the first andsecond flow faces 148, 150 of the filter construction 146. The rigidprojection 196, in the particular arrangement shown in FIG. 24, extendsaxially from the second flow face 150 of the filter construction 146.

[0100] The projection 196 shown has a pair of opposite sides 198, 102joined by an end tip 104. In preferred arrangements, one of the firstand second sides 198, 102 will provide a support or backing to the sealmember 192 such that seal 194 can be formed between and against theselected side 198 or 102 and the appropriate surface of the housing orduct. When this type of construction is used, the projection 196 will bea continuous member forming a closed hoop structure 106 (FIG. 22).

[0101] When this type of construction is used, a housing or duct maycircumscribe the projection 196 and hoop structure 106 including theseal member 192 to form seal 194 between and against the outer side 102of the projection 196 and an inner surface 110 of the housing or duct.

[0102] In the particular embodiment shown in FIG. 24, the seal member192 engages the end tip 104 of the projection 196 as well, such that theseal member 192 covers the projection 196 from the exterior side 102,over the end tip 104, and to the interior side 198.

[0103] Referring now to FIGS. 22 and 24, the frame 190 has a band,skirt, or depending lip 107 that is used to secure the frame 190 to themedia construction 146. The depending lip 107 depends or extends down afirst distance from cross braces 108.

[0104] During use of frames 190 of the type depicted herein, inwardforces are exerted around the circumference of the frame 190. Crossbraces 108 support the frame 190. By the term “support,” it is meantthat the cross braces 108 prevent the frame 190 from radially collapsingunder the forces exerted around the circumference of the frame 190.

[0105] The tip portion 104 provides support for the compressible sealmember 192. The compressible seal member 192 is preferably constructedand arranged to be sufficiently compressible to be compressed betweenthe tip portion 104 of the frame 190 and sidewall 110 of a housing orduct. When sufficiently compressed between the tip portion 104 and thesidewall 110, radial seal 194 is formed between the media pack 140 andthe sidewall 110.

[0106] One preferred configuration for seal member 192 is shown in FIG.25. The tip portion 104 of the flame 190 defines a wall or supportstructure between and against which radial seal 194 may be formed by thecompressible seal member 192. The compression of the compressible sealmember 192 at the sealing system 144 is preferably sufficient to form aradial seal under insertion pressures of no greater than 80 lbs.,typically, no greater than 50 lbs., for example, about 20-40 lbs., andlight enough to permit convenient and easy change out by hand.

[0107] In the preferred embodiment shown in FIG. 25, the seal member 192is a stepped cross-sectional configuration of decreasing outermostdimensions (diameter, when circular) from a first end 112 to a secondend 113, to achieve desirable sealing. Preferred specifications for theprofile of the particular arrangement shown in FIG. 25 are as follows: apolyurethane foam material having a plurality of (preferably at leastthree) progressively larger steps configured to interface with thesidewall 110 and provide a fluid-tight seal.

[0108] The compressible seal member 192 defines a gradient of increasinginternal diameters of surfaces for interfacing with the sidewall 110.Specifically, in the example shown in FIG. 25, the compressible sealmember 192 defines three steps 114, 115, 116. The cross-sectionaldimension or width of the steps 114, 115, 116 increases the further thestep 114, 115, 116 is from the second end 113 of the compressible sealmember 192. The smaller diameter at the second end 113 allows for easyinsertion into a duct or housing. The larger diameter at the first end112 ensures a tight seal.

[0109] In general, the media pack 140 can be arranged and configured tobe press-fit against the sidewall 110 of the housing 186 or duct. In thespecific embodiment shown in FIG. 24, the compressible seal member 192is compressed between the sidewall 110 and the tip portion 104 of theframe 190. After compression, the compressible seal member 192 exerts aforce against the sidewall 110 as the compressible seal member 192 triesto expand outwardly to its natural state, forming radial seal 94 betweenand against the tip portion 104 and the sidewall 110.

[0110] A variety of housings are usable with the media pack 140. In theparticular embodiment depicted in FIG. 24, the housing 186 includes abody member or a first housing compartment 118 and a removable cover orsecond housing compartment 120. In some arrangements, the first housingcompartment 118 is affixed to an object, such as a truck. The secondhousing compartment 120 is removably secured to the first housingcompartment 118 by a latching device 122.

[0111] In the illustrated embodiment in FIG. 24, the second end 150 ofthe media pack 140 with the attached frame 190 and compressible sealmember 192 is inserted into the first housing compartment 118. The mediapack 140 is press-fit into the first housing compartment 118 such thatthe compressible seal member 192 is compressed between and against thetip portion 104 of the frame 190 and the sidewall 110 of the firsthousing compartment 118, to form radial seal 194 therebetween.

[0112] During use of the arrangement depicted in FIG. 24, the fluidenters the housing assembly 185 at the inlet region 124 of the secondhousing compartment 120, in the direction shown at 187. The fluid passesthrough the filter construction 146. As the fluid passes through thefilter construction 146, contaminants are removed from the fluid. Thefluid exits the housing assembly 185 at the outlet region 128, in thedirection of 188. The compressible seal member 192 of the sealing system144 forms radial seal 194 to prevent contaminated fluid from exiting thehousing assembly 185, without first passing through the filterconstruction 146.

[0113]FIG. 26 is a perspective view of another embodiment of a mediapack 130. In the construction depicted, the media pack 130 includesfilter media 132 and a sealing system 134. The filter media 132 isdesigned to remove contaminants from a fluid, such as air, passingthrough the filter media 132. The sealing system 134 is designed to sealthe filter media 134 to a housing or duct.

[0114] The construction and geometry of the media pack 130 of FIGS.26-27, with the exception of preferred media formulations given inSection H below, is described in U.S. Pat. No. 6,190,432, which isincorporated by reference herein.

[0115] In certain preferred arrangements, the filter media 132 will beconfigured in a filter construction 136 with a first flow face 138 andan opposite, second flow face 140.

[0116] The filter construction 136 can have a variety of configurationsand cross-sectional shapes. In the particular embodiment illustrated inFIG. 26, the filter construction 136 has a non-circular cross-section.In particular, the FIG. 26 embodiment of the filter construction 136 hasan ob-round or “racetrack” cross-sectional shape. By “racetrack”cross-sectional shape, it is meant that the filter construction 136includes first and second semicircular ends 141, 142 joined by a pair ofstraight segments 143, 144.

[0117] In FIG. 26, certain portions 146 are depicted showing the flutes,including the open and closed ends. It should be understood that thisportion or section 146 is representative of the entire flow face 140 (aswell as the first flow face 138). For the sake of clarity andsimplicity, the flutes are not depicted in the other remaining portions149 of the flow face 140. Top and bottom plan views, as well as sideelevational views of the media pack 130 usable in the systems andarrangements described herein are depicted in copending and commonlyassigned U.S. patent application Ser. No. 29/101,193, filed Feb. 26,1999, and entitled, “Filter Element Having Sealing System,” herein andincorporated by reference.

[0118] As with the embodiment of FIG. 22, the media pack 130 includessealing system 134. In preferred constructions, the sealing system 134includes a flame 148 and a seal member 150.

[0119] The flame 148 has a non-circular, for example, obround and inparticular, a racetrack shape and is arranged and configured forattachment to the end of the filter media 132. In particular, the flame148 has a band or skirt or depending lip 151 that is generally racetrackshaped. The depending lip 151 depends or extends down a distance fromcross braces 152 and is used to secure the flame 148 to the media pack130.

[0120] During use of the arrangements depicted, inward forces areexerted around the circumference of the flame 148. Inward forces exertedagainst the semicircular ends 141, 142 can cause the straight segments143, 144 to bow or bend. Cross braces 152 are provided to providestructural rigidity and support to the straight segments 143, 144. Ascan be seen in FIG. 26, the particular cross braces 152 depicted form atruss system 154 between the opposing straight segments 143, 144. Thetruss system 154 includes a plurality of rigid struts 156, preferablymolded as a single piece with the remaining portions of the frame 148.

[0121] The frame 148 is constructed analogously to the frame 90. Assuch, the frame 148 includes a tip portion 158 (FIG. 27). In preferredarrangements, the tip portion 158 acts as an annular sealing support. Inpreferred systems, the compressible seal member 150 has structureanalogous to the that of the compressible seal member 92 of FIG. 5.

[0122] Preferably, the media pack 130 will be installed in a duct or anair cleaner housing. In FIG. 27, the housing depicted is a two-piecehousing including a cover 160 and a body member 162. The cover 160defines an airflow inlet 164. The body member 162 defines an airflowoutlet 166. The housing further includes a pre-cleaner arrangement 167upstream of the media pack 130, such as that described in U.S. Pat. Nos.2,887,177 and 4,162,906, incorporated by reference herein. In the onedepicted, the pre-cleaner arrangement 167 is in the cover 160. The cover160 includes a dust ejector 168 that expels dust and debris collected inthe pre-cleaner 167.

[0123] The compressible seal member 150 is compressed between thesidewall 170 and the tip portion 158 of the frame 150. As the media pack130 is press-fit, the compressible seal member 150 is compressed betweenand against the frame 148 (specifically, in the particular embodimentshown, the tip portion 158) and the sidewall 170. After compression, thecompressible seal member 150 exerts a force against the sidewall 170 asthe compressible seal member 150 tries to expand outwardly to itsnatural state, forming a radial seal 171 with the sidewall 170.

[0124] Preferred formulations for media 132 are described in Section H,below.

[0125] Another filter arrangement is shown in FIG. 28, generally at 174.With the exception of preferred media formulations described in SectionH below, the filter arrangement 174 is described in U.S. Pat. No.5,820,646, iincorporated by reference herein.

[0126] The filter arrangement 174 includes a media pack 176 mounted in,held by and supported by a panel construction 178. Filter arrangement174 also includes a housing 180, which includes a body 181 and aremovable cover member 182. The panel construction 178 holding the mediapack 176 seals within the housing 180, and is removable and replaceabletherefrom.

[0127] The media pack 176 includes fluted filter media 184 constructedas described above with respect to FIG. 23.

E. Typical System; Gas Turbine Air Intake

[0128] In FIG. 29, the air intake of a gas turbine system is showngenerally at 200. Airflow is shown drawn into an air intake system 200at arrows 201. The air intake system 200 includes a plurality of airfilter arrangements 202 generally held in a tube sheet 203. In preferredsystems, the tube sheet 203 will be constructed to hold the filterarrangements 202 at an angle, relative to a vertical axis. Preferredangles will be between 5-25°, for example, about 7°. This permits liquidto drain from the filter arrangements 202 when the system 200 is notoperating.

[0129] The air is cleaned in the air filter arrangements 202, and thenit flows downstream at arrows 204 into gas turbine generator 205, whereit is used to generate power.

[0130] In FIG. 33, an example of the air intake of a microturbine isillustrated generally at 210. In general, microturbines are smallerversions of gas turbines typically used as stand-by generators. In someinstances, such microturbines are approximately 24 inches by 18 inchesand have electrical power output typically between 30 kilowatts and 100kilowatts. These systems typically have air flow between 1000 cfm and10,000 cfm.

[0131] In FIG. 33, airflow is shown drawn into an air intake system 211at arrows 212. The air intake system 211 includes a filter arrangement213. As the air is drawn through the filter arrangement 213, the air iscleaned in the air filter arrangement 213, and then flows downstream atarrows 214 into a gas turbine 215. The gas turbine then typically powersan electrical generator, a fluid compressor, or a fluid pump. Asexplained below, constructing the filter arrangement in the form of acomposite of a barrier media and at least a single layer, and in someinstances, multiple layers of “fine fiber” can improve the performance(the operating efficiency, in particular) of the filter arrangement overprior art filters that are not constructed from such media composites.

F. Example Filter Arrangements for Gas Turbine Systems

[0132] One example of an air filter arrangement 202 usable in system 200or system 210 is shown in FIGS. 30-32. Other than preferred mediaformulations given in Section H, the air filter arrangement 202 isdescribed in commonly assigned U.S. Ser. No. 09/437,867, filed Nov. 10,1999, incorporated by reference herein. In general, the air filterarrangement 202 includes a first, or primary filter element 220 (FIGS.30 and 32) and a second filter element 222 (FIGS. 31 and 32), which actsas a prefilter. By the term “prefilter”, it is meant a separator that ispositioned upstream of the main, primary filter element 220, thatfunctions to remove large particles from the gas stream. The primaryfilter element 220 and the prefilter element 222 are preferably securedwithin a sleeve member 224 that is removably mountable in an aperture226 in tube sheet 203. In general, air flow is taken into the system 200and flows first through the prefilter element 222 and then through theprimary filter element 220. After exiting the primary filter element220, the air is directed into the generator 205.

[0133] In general, the element 220 is constructed from fluted orz-shaped media 230, as described above in connection with FIGS. 2 and 3.In FIG. 30, it should be understood that the outlet face 228 is shownschematically. That is, only a portion of the face 228 is shown withflutes. It should be understood that, in typical systems, the entireface 228 will be fluted.

[0134] The filter element 220 has a first end 232 and an opposite,second end 234. In the arrangement depicted in FIG. 30, the first end232 will correspond to an upstream end inlet face 227, while the secondend 234 will correspond to a downstream end outlet face 228. Thestraight through flow allows gas to flow into the first end 232 and exitthe second end 234, such that the direction of the air flow into thefirst end 232 is the same direction of air flow that is exiting thesecond end 234. Straight through flow patterns can reduce the amount ofturbulence in the gas flow.

[0135] The media 230 can be a polyester synthetic media, a media madefrom cellulose, or blends of these types of materials and treated withfine fiber.

[0136] Preferably, the prefilter element 222 is a pleated construction236 comprising a plurality of individual pleats 237. The pleats 237 arearranged in a zig-zag fashion. Preferred prefilter elements 222 willhave a generally circular cross-section.

[0137] The prefilter element 222 is configured to permit straightthrough flow. In other words, the air flows directly through theprefilter element 222, entering at an inlet face 238 and exiting at anoppositely disposed outlet face 239, wherein the direction of fluid flowentering the inlet face 238 is in the same direction of fluid flowexiting the outlet face 239.

[0138] In certain preferred embodiments, there will be at least 15pleats 237, no greater than 80 pleats 237, and typically 30-50 pleats237. The pleated construction 236 is made from a media 240 that isfolded in the form of pleats 237 centered around a central core 241.Useable types of media 240 includes fiberglass, or alternatively, an airlaid media. Specific properties of usable media 240 include: a dry laidfilter medium made from polyester fibers randomly oriented to form a webhaving a weight of 2.7-3.3 oz./yd³ (92-112 g/m³); a free thickness(i.e., thickness at 0.002 psi compression) of 0.25-0.40 in. (6.4-10.2mm); and a permeability of at least 400 ft./min (122 m/min).

[0139] In general, the prefilter element 222 is removably andreplaceably mountable in the sleeve member 224. The sleeve member 224 isdescribed in further detail below. In certain systems, the prefilterelement 222 is held within the sleeve member 224 by squeezing orcompressing end tips of the media 240 against the inside wall of thesleeve member 224.

[0140] Preferred filter arrangements 202 constructed according toprinciples herein will have sleeve member 224 secured to andcircumscribing the primary filter element 220. In general, the sleevemember 224 functions to hold the primary element 220 in place in thesystem 200. Preferred sleeve members 224 will also hold the prefilterelement 222 in place upstream of the primary element 220.

[0141] As can be seen in FIGS. 30 and 31, the sleeve member 224preferably has a cross-section that matches the cross-section of theprimary filter element. The sleeve member 224 includes a surroundingwall 244 that is curved in a form to result in a surrounding ring 245.The sleeve member 224 is preferably oriented relative to the primaryfilter element 220 to extend at least 30% of the axial length of theprimary filter element 220. In many typical arrangements, the sleevemember 224 will extend greater than 50% of the axial length of theprimary filter element 220. Indeed, in most preferred arrangements, thesleeve member 224 will extend at least the entire length (that is, 100%)of the axial length of the primary filter element 220. In many typicalapplications, the sleeve member 224 will have a radius of at least 10inches, typically 15-30 inches, and in some instances, no greater than50 inches.

[0142] The sleeve member 224 is preferably constructed and arranged witha sealing system to allow for securing the primary filter element 220 tothe tube sheet 203, to inhibit air from bypassing the primary element220. In the illustrated embodiment, the sleeve member 224 includes aseal member pressure flange 246. The flange 246 at least partially, andin many embodiments fully, circumscribes the wall 244 of the sleevemember 224. The seal member pressure flange 246 operates as a backstopto support a seal member 248 in order to create a seal 250 between andagainst the flange 246 and the tube sheet 203. The flange 246 extendsradially from the wall 244 of the sleeve member 224 and fullycircumscribes the seal member 224. The flange 246 will extend radiallyfrom the wall 244 a distance sufficient to support the seal member 248.

[0143] A patch or retaining clip 252 (FIG. 30) extends over ajoint 254to secure the sleeve member 224 in its final configuration Preferably,the retaining clip 252 is secured in a permanent way to the sleevemember 224; for example, by ultrasonic welding.

[0144] Attention is directed to FIG. 32. It can be seen that the flange246 supports the seal member 248 on the axial side 256. The seal member248 generally comprises a circular gasket 258. The gasket 258 ispreferably secured to the flange 246, by adhesive between the gasket 258and the side 256 of the flange 246. The gasket 258 is positioned on theflange 246, such that the gasket 258 completely circumscribes the wall244 and the primary element 220.

[0145] The arrangement depicted also includes a system for clamping thesleeve member 224 to the tube sheet 203. In the illustrated embodiment,the clamping system includes a plurality of latches or clamps 260. Thereshould be enough latches or clamps 260 to form a good, tight seal 250between the flange 246 and the tube sheet 203, when the sleeve member224 is operably installed in the tube sheet 203; for example,illustrated is 4 clamps 260. In FIG. 32, the clamp 260 is shown incross-section. Each of the clamps 260 includes a lever 261, a nose 262,and a plate 263. The plate 263 includes apertures for accommodating afastener, such as a bolt 264 to secure the clamp 260 to the tube sheet203. The nose 262 operates to apply pressure to the flange 246 andcompress the seal member 248 against the tube sheet 203. The lever 261operates to selectively move the nose 262 toward and away from the tubesheet 203. In other embodiments, the clamps 260 can be hand-tightened,such as using wing nuts.

[0146] In typical operation, there is an overall pressure drop acrossthe filter arrangement 202 of about 0.6-1.6 inches of water. Thisincludes both the primary filter element 220 and the prefilter 222.Typically, the pressure drop across the prefilter 222 alone will beabout 0.2-0.6 inches of water, while the pressure drop across theprimary element 220 alone will be about 0.4-1 inch of water.

[0147] Another example of an air filter arrangement 213 usable in thesystem 304 or system 302 is shown in FIGS. 34-36. With the exception ofpreferred media formulations provided in Section H below, the air filterarrangement is described in commonly assigned U.S. patent applicationSer. No. 09/593,257 filed Jun. 13, 2000, incorporated by referenceherein.

[0148]FIG. 35 illustrates the filter arrangement 213 in an exploded,unassembled form, while FIG. 14 illustrates the filter arrangement 213assembled for use. In general, the air filter arrangement 213 includes amoisture separator 270, a filter assembly 272, and a filter housing 274.The filter housing 274 is typically secured within a tube sheet 276 whenassembled for use. Preferably, the filter housing 274 is secured withinthe tube sheet 276 by welding the housing 274 to the tube sheet 276 orby bolting the housing 274 to the tube sheet 276.

[0149] An access door 278 provides access to the filter arrangement 213when assembled and allows air to be drawn into the system 302. Ingeneral, the access door 278 is designed and constructed to fit theparticular housing of the system, such as the system 302, of FIG. 33, itis to be installed in and to provide access to the filter arrangement213, when assembled. The access door 278 is also designed andconstructed to allow air to enter the system 210, FIG. 33.

[0150] The access door 278 preferably includes an air flow resistancearrangement 280. In general, the air flow resistance arrangement 280directs air flow into the filter arrangement 213 in a particulardirection to reduce resistance through the system 302. The air flowresistance arrangement 280 also aids in noise attenuation. In theembodiment depicted in FIG. 34, the air flow resistance arrangement isdepicted as a plurality of louvers 282. The louvers 282 also aid inprotecting the system 210 from entry of large objects and moisture intothe system 302, FIG. 33. The louvers 282 further aid in noiseattenuation.

[0151] Moisture in the incoming air stream can damage the integrity ofthe filter assembly 272, and damage, i.e. contribute to rusting, theinternal mechanisms of the system 302. To address this, the filterarrangement includes moisture separator 270. In general, the moistureseparator 270 separates and collects moisture from the incoming airstream prior to reaching the filter assembly 272. In one embodiment, themoisture separator 270 includes a plurality of flat screens, e.g., wiremesh.

[0152] In general, the filter assembly 272 removes contaminants from theincoming air stream 212, FIG. 33, prior to entry into the internalmechanisms of the system 302. Preferably, the filter assembly 272 isconfigured to permit straight through flow directly through the filterassembly 272, entering at an inlet face 284 and exiting at an oppositelydisposed outlet face 285, wherein the direction of fluid flow enteringthe inlet face 284 is in the same direction of fluid flow exiting theoutlet face 285.

[0153] The filter assembly 272 includes a media pack 286 formed fromfluted media 288 rolled into a cylinder, as explained above inconnection with FIGS. 22 and 23. The media 288 can be a polyestersynthetic media, a media made from cellulose, or blends of these typesof materials and treated with a coating or a layer of fine fiber.Preferred media formulations are given in Section H below.

[0154] The filter assembly 272 depicted includes a pull mechanism 290.The pull mechanism 290 is constructed to allow a user to easily removethe filter assembly 272 from the filter housing 274. In the one shown,the pull mechanism 290 includes a handle 292 and a retention mechanism294 (FIG. 34). Typically, the handle 292 is a knob 296. In the one shownin FIG. 34, the retention mechanism 294 includes a bolt 298 attached tothe knob 296 and a nut 299 at the other end of the bolt. Alternatively,the pull mechanism and the core of the filter media could be oneintegrated unit.

[0155] In general, the filter housing 274 is constructed to receive andhold the filter assembly 272 and to facilitate sealing with the filterassembly 272. In the one shown in FIG. 16, the filter housing 274includes a transition area 302 angled from an outer wall 304 at an angleof at least 10 degrees, preferably between 10 and 210 degrees, and mostpreferably about 15 degrees. The transition area 302 aids in sealing thefilter assembly 272 as will be explained in more detail below.

[0156] The filter housing 274 further includes a mounting flange 306.The mounting flange 306 secures the filter housing 274 to the tube sheet276 through a fastener arrangement (e.g., bolts). The housing 274 alsoincludes a stopping arrangement 308. The stopping arrangement 308 seatsthe filter assembly 272 within the housing 274 to prevent the filterassembly 272 from being pushed too far into the housing 274. Thestopping arrangement 308 also helps in ensuring a proper seal betweenthe filter assembly 272 and the housing 274.

[0157] The stopping arrangement 308 includes a stop 310. Preferably, thestop 310 projects from the outer wall 304 a distance sufficient toprevent the filter assembly 272 from bypassing the stop 310. During use,the filter assembly 272 rests upon a top surface 311 of the stop 310.

[0158] The filter assembly 272 also includes a sealing gasket 312. Thesealing gasket 312 seals the filter assembly 272 in the filter housing274, inhibiting air from entering the system 302 between the filterassembly 272 and the filter housing 274 and bypassing the filterassembly 272. This ensures that the air stream goes substantiallythrough the filter assembly 272. In the one illustrated, the sealinggasket 312 extends circumferentially around the radial edge of thefilter assembly 272. In one embodiment, the sealing gasket 312 comprisesclosed cell foam; of course, the sealing gasket 312 can comprise othersuitable material.

[0159] During use, the sealing gasket 312 seals ajoint 314 between thefilter assembly 272 and the filter housing 274. During installation, thefilter assembly 272 is inserted into the housing 274 until an end 315rests against the stop 310. As the filter assembly 272 is installed, thesealing gasket 312 is compressed in the transition area 302 between thefilter assembly 272 and the housing 274, sealing the joint 314.

[0160] During assembly, the filter housing 274 is slid into the tubesheet 276 until the mounting flange 306 of the filter housing 274 isseated against the tube sheet 276. Next, the filter assembly 272 isseated within the filter housing 274. The filter assembly 272 is slidinto the filter housing 274 until the end 315 of the filter assembly 272rests against the stop 310. The sealing gasket 312 is partiallycompressed and the filter assembly 272 is snugly held with the filterhousing 274.

[0161] In operation, the filter arrangement 213 is used as follows: Airto be filtered in the system 302 is directed at arrows 212 into theintake system 211. The air flows through the filter assembly 272. Theair enters at the inlet face 284, passes through the fluted construction288, and exits through the outlet face 285. From there, the air is takeninto the turbine or generator 215.

G. Typical System; Fuel Cell Air Intake

[0162] A fuel cell air intake is shown schematically in FIG. 37 at 330.As depicted in FIG. 37, atmospheric or ambient air 331 enters filterassembly 332 via an inlet 333. Prior to entering filter assembly 332,atmospheric air 331 is dirty air having various physical (e.g.,particulate) and chemical contaminants. Filter assembly 332 isconstructed to remove various contaminants from the dirty air to provideclean air 334 that exits from filter assembly 332. Clean air 334 is theintake air for a fuel cell 335, used to generate power.

[0163] Referring still to FIG. 37, atmospheric air 331 enters filterassembly 332 as dirty air through inlet 333 in housing 336 andprogresses to dirty air side 337 of filter element 338. As the airpasses through filter element 338 to clean air side 339, contaminantsare removed by filter element 338 to provide filtered air 334. Filteredair 334 exits filter assembly 332 through outlet 340 of housing 336 andis used by equipment 341.

[0164] Filter assembly 332 also optionally includes a noise suppressionelement 342 to reduce or suppress the level of noise or sound emanatingfrom equipment 341. Suppression element 342 may be positioned withinhousing 336, and in some embodiments, suppression element 342 is definedby housing 336.

[0165] Equipment 341 includes a compressor 343 that provides air to fuelcell 335 to use in its catalytic reaction. Compressor 343 emits noise,typically in the range of 3 Hertz to 30,000 Hertz, sometimes as high as50,000 Hertz, at a level of 85 to 110 dB at one meter. Suppressionelement 342, reduces the level of sound traveling upstream fromcompressor 343 by at least 3 dB, typically by at least 6 dB, andpreferably by at least 25 dB.

[0166] The fuel cell 335 takes in hydrogen fuel 345, emits a by-productof water and carbon dioxide 346, and generates power 347. In general,fuel cells are devices consisting of two electrodes (an anode and acathode) that sandwich an electrolyte. A fuel containing hydrogen flowsto the anode, where the hydrogen electrons are freed, leaving positivelycharged ions. The electrons travel through an external circuit in whichthe ions diffuse through the electrolyte. At the cathode, the electronscombine with the hydrogen ions and oxygen to form water and carbondioxide, by-products. A common oxygen source is air. To speed thecathodic reaction, a catalyst is often used. Examples of catalysts oftenused in the fuel cell reaction include nickel, platinum, palladium,cobalt, cesium, neodymium, and other rare earth metals. The reactants inthe fuel cell are the hydrogen fuel and an oxidizer.

[0167] Typically, “low temperature fuel cells” operate at temperatures,typically about 70 to 100° C., sometimes as high as 200° C. Hightemperature fuel cells are typically not as sensitive to chemicalcontamination due to their higher operating temperature. Hightemperature fuel cells are, however, sensitive to particulatecontamination, and some forms of chemical contamination, and thus hightemperature fuel cells benefit from the filtering features as describedherein. One type of low temperature fuel cell is commonly referred to asa “PEM”, is named for its use of a proton exchange membrane. Examples ofother various types of fuel cells that can be used in combination withthe filter assembly of the present invention include, for example, U.S.Pat. Nos. 6,110,611; 6,117,579; 6,103,415; and 6,083,637, thedisclosures of which are incorporated here by reference. Various fuelcells are commercially available from, for example, Ballard PowerSystems, Inc. of Vancouver, Canada; International Fuel Cells, ofConnecticut; Proton Energy Systems, Inc. of Rocky Hill, Conn.; AmericanFuel Cell Corp. of Massachusetts; Siemans AG of Erlangen, Germany;Energy Partners, L.C. of Florida; General Motors of Detroit, Mich.; andToyota Motor Corporation of Japan.

[0168] The filter assemblies, as described below, remove contaminantsfrom the atmospheric air before the air is used in the fuel celloperation. As explained below, constructing the filter assembly in theform of a composite of a barrier media and at least a single layer, andin some instances, multiple layers of “fine fiber” can enhance theperformance (the operating efficiency, in particular) of the filterassembly. The fine fiber treatment is advantageous in improving filterefficiency in most filter geometry and environment. In certain harshenvironments with a filter temperature over 120° F., which includes bothlow temperature and high temperature fuel cells the fine fiber can oftensurvive and provide extended lifetime filtration.

H. Example Filter Arrangement for Fuel Cell Air Intake Systems

[0169]FIG. 38 illustrates a filter assembly 350 usable in the system ofFIG. 37. Filter assembly 350 includes a housing 352 which defines aninlet 354 and an outlet 356. Dirty air enters filter assembly 350 viainlet 354, and clean air exits via outlet 356.

[0170] Positioned within housing 352 is a filter element 358 and a noisesuppression element 360. Suppression element 360 comprises a firstresonator 361 and a second resonator 362. First resonator 361 isconfigured to attenuate a peak of about 900 Hz, and second resonator 362is configured to attenuate a peak of about 550 Hz.

[0171] Filter element 358 of FIG. 38 is generally constructedanalogously as the filter element construction 40 (FIG. 22). As such, itincludes a media pack 364 of fluted media 366 (as described with respectto FIG. 3) rolled into filter element 358.

[0172] When filter element 358 is used with inline-flow housing 352, theair will enter through inlet 354 of housing 352 in one direction, enterfilter element 358 through first flow face 368 in the same direction,exit filter element 358 in the same direction from second flow face 370,and exit housing 352 through outlet 356 also in the same direction.

[0173] As with the embodiment of FIGS. 22 and 24, a radial seal 372 isformed by compression of the sealing gasket 374 between and against aframe 376 and an inner sealing surface 378 of the housing.

[0174] Filter assembly 350 preferably also includes a portion designedto remove contaminants from the atmosphere by either adsorption orabsorption. As used herein, the terms “adsorb”, “adsorption”,“adsorbent” and the like, are intended to also include the mechanisms ofabsorption and adsorption.

[0175] The chemical removal portion typically includes a physisorbent orchemisorbent material, such as, for example, desiccants (i.e., materialsthat adsorb or absorb water or water vapor) or materials that adsorb orabsorb volatile organic compounds and/or acid gases and/or basic gases.The terms “adsorbent material,” “adsorption material,” “adsorptivematerial,” “absorbent material,” absorption material,” absorptivematerial,” and any variations thereof, are intended to cover anymaterial that removes chemical contaminants by adsorption or absorption.Suitable adsorbent materials include, for example, activated carbon,activated carbon fibers, impregnated carbon, activated alumina,molecular sieves, ion-exchange resins, ion-exchange fibers, silica gel,alumina, and silica. Any of these materials can be combined with, coatedwith, or impregnated with materials such as potassium permanganate,calcium carbonate, potassium carbonate, sodium carbonate, calciumsulfate, citric acid, or mixtures thereof. In some embodiments, theadsorbent material can be combined or impregnated with a secondmaterial.

[0176] The adsorbent material typically includes particulates orgranulated material and can be present as granules, beads, fibers, finepowders, nanostructures, nanotubes, aerogels, or can be present as acoating on a base material such as a ceramic bead, monolithicstructures, paper media, or metallic surface. Typically, the adsorbentmaterials, especially particulate or granulated materials, are providedas a bed of material.

[0177] Alternately, the adsorbent material can be shaped into amonolithic or unitary form, such as a large tablet, granule, bead, orpleatable or honeycomb structure that optionally can be further shaped.In at least some instances, the shaped adsorbent material substantiallyretains its shape during the normal or expected lifetime of the filterassembly. The shaped adsorbent material can be formed from afree-flowing particulate material combined with a solid or liquid binderthat is then shaped into a non-free-flowing article. The shapedadsorbent material can be formed by, for example, a molding, acompression molding, or an extrusion process. Shaped adsorbent articlesare taught, for example, in U.S. Pat. No. 5,189,092 (Koslow), and U.S.Pat. No. 5,331,037 (Koslow), which are incorporated herein by reference.

[0178] The binder used for providing shaped articles can be dry, thatis, in powdered and/or granular form, or the binder can be a liquid,solvated, or dispersed binder. Certain binders, such as moisture curableurethanes and materials typically referred to as “hot melts”, can beapplied directly to the adsorbent material by a spray process. In someembodiments, a temporary liquid binder, including a solvent ordispersant which can be removed during the molding process, is used.Suitable binders include, for example, latex, microcrystallinecellulose, polyvinyl alcohol, ethylene-vinyl acetate, starch, carboxylmethyl cellulose, polyvinylpyrrolidone, dicalcium phosphate dihydrate,and sodium silicate. Preferably the composition of a shaped materialincludes at least about 70%, by weight, and typically not more thanabout 98%, by weight, adsorbent material. In some instances, the shapedadsorbent includes 85 to 95%, preferably, approximately 90%, by weight,adsorbent material. The shaped adsorbent typically includes not lessthan about 2%, by weight, binder and not more than about 30%, by weight,binder.

[0179] Another embodiment of a suitable adsorbent material for use inthe chemical removal portion is an adsorbent material that includes acarrier. For example, a mesh or scrim can be used to hold the adsorbentmaterial and binder. Polyester and other suitable materials can be usedas the mesh or scrim. Typically, any carrier is not more than about 50%of the weight of the adsorbent material, and is more often about 20 to40% of the total adsorbent weight. The amount of binder in the shapedadsorbed article with the carrier typically ranges about 10 to 50% ofthe total adsorbent weight and the amount of adsorbent materialtypically ranges about 20 to 60% of the total adsorbent weight.

[0180] The chemical removal portion can include strongly basic materialsfor the removal of acid contaminants from the air, or strongly acidicmaterials for the removal of basic contaminants from the air, or both.Preferably, the basic materials and acidic materials are removed fromeach other so that they do not cancel each other. In some embodiments,the adsorbent material itself may be the strongly acidic or strong basicmaterial. Examples of such materials include materials such as polymerparticulates, activated carbon media, zeolites, clays, silica gels, andmetal oxides. In other embodiments, the strongly acidic materials andthe strongly basic materials can be provided as surface coatings oncarriers such as granular particulate, beads, fibers, fine powders,nanotubes, and aerogels. Alternately or additionally, the acidic andbasic material that forms the acidic and basic surfaces may be presentthroughout at least a portion of the carrier; this can be done, forexample, by coating or impregnating the carrier material with the acidicor basic material.

[0181] Both basic and acidic materials may be present in the chemicalremoval portion of the filter element; however, it is preferable thatthe two types of materials are spaced from each other so that they donot react with and neutralize one another. In some embodiments, thebasic material, acidic material, or both, may be spaced from anadsorbent material, such as activated carbon.

[0182] Examples of acidic compounds that are often present inatmospheric air and are considered as contaminants for fuel cellsinclude sulfur oxides, nitrogen oxides, hydrogen sulfide, hydrogenchloride, and volatile organic acids and nonvolatile organic acids.Examples of basic compounds that are often present in atmospheric airand are considered as contaminants for fuel cells include ammonia,amines, amides, sodium hydroxides, lithium hydroxides, potassiumhydroxides, volatile organic bases and nonvolatile organic bases.

[0183] For PEM fuel cells, the cathodic reaction occurs under acidicconditions, thus, it is undesirable to have basic contaminants present.An example of a preferred material for removing basic contaminants, suchas ammonia, is a bed of activated carbon granules impregnated withcitric acid.

[0184] A second example of a filter assembly usable in the system ofFIG. 37 is shown in fragmented cross-section in FIG. 39 as a filterassembly 380. Filter assembly 380 includes a housing 382 which definesan inlet 384 and an outlet 386. Dirty air enters filter assembly 380 viainlet 384, and clean air exits via outlet 386. Sound suppression element388 comprises a resonator 390. A filter element 391 is mounted withinthe housing 382 and is analogous to filter element 358.

[0185] Filter assembly 380 also includes an adsorbent element 392.Adsorbent element 392 comprises a cylindrical mass of carbon 393 betweenends 394,395. In the one depicted, mass of carbon 393 is a hollow,circular extension 397 of activated carbon held together by athermoplastic binder. Carbon 393 can be produced, for example, by theteachings of U.S. Pat. No. 5,189,092 (Koslow), and U.S. Pat. No.5,331,037 (Koslow). Positioned at first end 394 is a sealing system 396and positioned at second end 395 is a cap 398.

[0186] Sealing system 396 provides an air-tight seal between adsorbentelement 392 and baffle 401. Sealing system 396 is designed to sealadsorbent element 392 against baffle 401, and, under normal conditions,inhibit air from passing through a region between adsorbent element 392and the sidewall of housing 382. Sealing system 396 inhibits air flowfrom avoiding passing through carbon 393 of adsorbent element 392.Sealing system 396 is typically made from a flexible, compressiblematerial, such as polyurethane.

[0187] Cap 398 diverts air exiting filter element 358 so that it entersadsorbent element 392 through carbon 393 rather than passing axiallythrough the cylindrical extension of carbon 393. Air from filter element391 impinges on an exposed surface 402 of cap 398 and is rerouted fromits “straight-line” flow to a flow having a radial component. Cap 398includes apertures 404 therein for passage of air through cap 398 sothat the air can reach carbon 393. In addition to managing air flow, cap398 provides anchoring of absorbent element 392 to filter element 391.

[0188] Adsorbent element 392 functions both as a chemical removalportion and as an element of sound suppression element 388. Otherarrangements of adsorbent elements and adsorbent materials may also haveboth a chemical removal quality and a sound suppression quality.

I. Preferred Media Construction for Filter Elements Disclosed Above

[0189] A fine fiber filter structure includes a bi-layer or multi-layerstructure wherein the filter contains one or more fine fiber layerscombined with or separated by one or more synthetic, cellulosic orblended webs. Another preferred motif is a structure including finefiber in a matrix or blend of other fibers.

[0190] We believe important characteristics of the fiber and microfiberlayers in the filter structure relate to temperature resistance,humidity or moisture resistance and solvent resistance, particularlywhen the microfiber is contacted with humidity, moisture or a solvent atelevated temperatures. Further, a second important property of thematerials of the invention relates to the adhesion of the material to asubstrate structure. The microfiber layer adhesion is an importantcharacteristic of the filter material such that the material can bemanufactured without delaminating the microfiber layer from thesubstrate, the microfiber layer plus substrate can be processed into afilter structure including pleats, rolled materials and other structureswithout significant delamination. We have found that the heating step ofthe manufacturing process wherein the temperature is raised to atemperature at or near but just below melt temperature of one polymermaterial, typically lower than the lowest melt temperature substantiallyimproves the adhesion of the fibers to each other and the substrate. Ator above the melt temperature, the fine fiber can lose its fibrousstructure. It is also critical to control heating rate. If the fiber isexposed to its crystallization temperature for extended period of time,it is also possible to lose fibrous structure. Careful heat treatmentalso improved polymer properties that result from the formation of theexterior additive layers as additive materials migrate to the surfaceand expose hydrophobic or oleophobic groups on the fiber surface.

[0191] The criteria for performance is that the material be capable ofsurviving intact various operating temperatures, i.e. a temperature of140° F., 160° F., 270° F., 300° F. for a period of time of 1 hour or 3hours, depending on end use, while retaining 30%, 50%, 80% or 90% offilter efficiency. An alternative criteria for performances that thematerial is capable of surviving intact at various operatingtemperatures, i.e. temperatures of 140° F., 160° F., 270° F., 300° F.,for a period of time of 1 hours or 3 hours depending on end use, whileretaining, depending on end use, 30%, 50%, 80% or 90% of effective finefibers in a filter layer. Survival at these temperatures is important atlow humidity, high humidity, and in water saturated air. The microfiberand filter material of the invention are deemed moisture resistant wherethe material can survive immersion at a temperature of greater than 160°F. while maintaining efficiency for a time greater than about 5 minutes.Similarly, solvent resistance in the microfiber material and the filtermaterial of the invention is obtained from a material that can survivecontact with a solvent such as ethanol, a hydrocarbon, a hydraulicfluid, or an aromatic solvent for a period of time greater than about 5minutes at 70° F. while maintaining 50% efficiency.

[0192] The fine fiber materials of the invention can be used in avariety of filter applications including pulse clean and non-pulsecleaned filters for dust collection, gas turbines and engine air intakeor induction systems; gas turbine intake or induction systems, heavyduty engine intake or induction systems, light vehicle engine intake orinduction systems; vehicle cabin air; off road vehicle cabin air, diskdrive air, photocopier-toner removal; HVAC filters in both commercial orresidential filtration applications. Paper filter elements are widelyused forms of surface loading media In general, paper elements comprisedense mats of cellulose, synthetic or other fibers oriented across a gasstream carrying particulate material. The paper is generally constructedto be permeable to the gas flow, and to also have a sufficiently finepore size and appropriate porosity to inhibit the passage of particlesgreater than a selected size therethrough. As the gases (fluids) passthrough the filter paper, the upstream side of the filter paper operatesthrough diffusion and interception to capture and retain selected sizedparticles from the gas (fluid) stream. The particles are collected as adust cake on the upstream side of the filter paper. In time, the dustcake also begins to operate as a filter, increasing efficiency. This issometimes referred to as “seasoning,” i.e. development of an efficiencygreater than initial efficiency.

[0193] A simple filter design such as that described above is subject toat least two types of problems. First, a relatively simple flaw, i.e.rupture of the paper, results in failure of the system. Secondly,particulate material rapidly builds up on the upstream side of thefilter, as a thin dust cake or layer, increasing the pressure drop.Various methods have been applied to increase the “lifetime” ofsurface-loaded filter systems, such as paper filters. One method is toprovide the media in a pleated construction, so that the surface area ofmedia encountered by the gas flow stream is increased relative to aflat, non-pleated construction. While this increases filter lifetime, itis still substantially limited. For this reason, surface loaded mediahas primarily found use in applications wherein relatively lowvelocities through the filter media are involved, generally not higherthan about 20-30 feet per minute and typically on the order of about 10feet per minute or less. The term “velocity” in this context is theaverage velocity through the media (i.e. flow volume per media area).

[0194] In general, as air flow velocity is increased through a pleatedpaper media, filter life is decreased by a factor proportional to thesquare of the velocity. Thus, when a pleated paper, surface loaded,filter system is used as a particulate filter for a system that requiressubstantial flows of air, a relatively large surface area for the filtermedia is needed. For example, a typical cylindrical pleated paper filterelement of an over-the-highway diesel truck will be about 9-15 inches indiameter and about 12-24 inches long, with pleats about 1-2 inches deep.Thus, the filtering surface area of media (one side) is typically 30 to300 square feet.

[0195] In many applications, especially those involving relatively highflow rates, an alternative type of filter media, sometimes generallyreferred to as “depth” media, is used. A typical depth media comprises arelatively thick tangle of fibrous material. Depth media is generallydefined in terms of its porosity, density or percent solids content. Forexample, a 2-3% solidity media would be a depth media mat of fibersarranged such that approximately 2-3% of the overall volume comprisesfibrous materials (solids), the remainder being air or gas space.

[0196] Another useful parameter for defining depth media is fiberdiameter. If percent solidity is held constant, but fiber diameter(size) is reduced, pore size or interfiber space is reduced; i.e. thefilter becomes more efficient and will more effectively trap smallerparticles.

[0197] A typical conventional depth media filter is a deep, relativelyconstant (or uniform) density, media, i.e. a system in which thesolidity of the depth media remains substantially constant throughoutits thickness. By “substantially constant” in this context, it is meantthat only relatively minor fluctuations in density, if any, are foundthroughout the depth of the media. Such fluctuations, for example, mayresult from a slight compression of an outer engaged surface, by acontainer in which the filter media is positioned.

[0198] Gradient density depth media arrangements have been developed.some such arrangements are described, for example, in U.S. Pat. Nos.4,082,476; 5,238,474; and 5,364,456. In general, a depth mediaarrangement can be designed to provide “loading” of particulatematerials substantially throughout its volume or depth. Thus, sucharrangements can be designed to load with a higher amount of particulatematerial, relative to surface loaded systems, when full filter lifetimeis reached. However, in general the tradeoff for such arrangements hasbeen efficiency, since, for substantial loading, a relatively lowsolidity media is desired. Gradient density systems such as those in thepatents referred to above, have been designed to provide for substantialefficiency and longer life. In some instances, surface loading media isutilized as a “polish” filter in such arrangements.

[0199] A filter media construction according to the present inventionincludes a first layer of permeable coarse fibrous media or substratehaving a first surface. A first layer of fine fiber media is secured tothe first surface of the first layer of permeable coarse fibrous media.Preferably the first layer of permeable coarse fibrous materialcomprises fibers having an average diameter of at least 10 microns,typically and preferably about 12 (or 14) to 30 microns. Also preferablythe first layer of permeable coarse fibrous material comprises a mediahaving a basis weight of no greater than about 200 grams/meter²,preferably about 0.50 to 150 g/m², and most preferably at least 8 g/m².Preferably the first layer of permeable coarse fibrous media is at least0.0005 inch (12 microns) thick, and typically 0.0006 to 0.02 (15 to 500microns) thick and preferably is about 0.001 to 0.030 inch (25-800microns) thick.

[0200] In preferred arrangements, the first layer of permeable coarsefibrous material comprises a material which, if evaluated separatelyfrom a remainder of the construction by the Frazier permeability test,would exhibit a permeability of at least 1 meter(s)/min, and typicallyand preferably about 2-900 meters/min. Herein when reference is made toefficiency, unless otherwise specified, reference is meant to efficiencywhen measured according to ASTM-1215-89, with 0.7811 monodispersepolystyrene spherical particles, at 20 fpm (6.1 meters/min) as describedherein.

[0201] Preferably the layer of fine fiber material secured to the firstsurface of the layer of permeable coarse fibrous media is a layer ofnano- and microfiber media wherein the fibers have average fiberdiameters of no greater than about 2-microns, generally and preferablyno greater than about 1 micron, and typically and preferably have fiberdiameters smaller than 0.5 micron and within the range of about 0.05 to0.5 micron. Also, preferably the first layer of fine fiber materialsecured to the first surface of the first layer of permeable coarsefibrous material has an overall thickness that is no greater than about30 microns, more preferably no more than 20 microns, most preferably nogreater than about 10 microns, and typically and preferably that iswithin a thickness of about 1-8 times (and more preferably no more than5 times) the fine fiber average diameter of the layer.

[0202] Certain preferred arrangements according to the present inventioninclude filter media as generally defined, in an overall filterconstruction. Some preferred arrangements for such use comprise themedia arranged in a cylindrical, pleated configuration with the pleatsextending generally longitudinally, i.e. in the same direction as alongitudinal axis of the cylindrical pattern. For such arrangements, themedia may be imbedded in end caps, as with conventional filters. Sucharrangements may include upstream liners and downstream liners ifdesired, for typical conventional purposes.

[0203] In some applications, media according to the present inventionmay be used in conjunction with other types of media, for exampleconventional media, to improve overall filtering performance orlifetime. For example, media according to the present invention may belaminated to conventional media, be utilized in stack arrangements; orbe incorporated (an integral feature) into media structures includingone or more regions of conventional media. It may be used upstream ofsuch media, for good load; and/or, it may be used downstream fromconventional media, as a high efficiency polishing filter.

[0204] Certain arrangements according to the present invention may alsobe utilized in liquid filter systems, i.e. wherein the particulatematerial to be filtered is carried in a liquid. Also, certainarrangements according to the present invention may be used in mistcollectors, for example arrangements for filtering fine mists from air.

[0205] According to the present invention, methods are provided forfiltering. The methods generally involve utilization of media asdescribed to advantage, for filtering. As will be seen from thedescriptions and examples below, media according to the presentinvention can be specifically configured and constructed to providerelatively long life in relatively efficient systems, to advantage.

[0206] Various filter designs are shown in patents disclosing andclaiming various aspects of filter structure and structures used withthe filter materials. Engel et al., U.S. Pat. No. 4,720,292, disclose aradial seal design for a filter assembly having a generally cylindricalfilter element design, the filter element being sealed by a relativelysoft, rubber-like end cap having a cylindrical, radially inwardly facingsurface. Kahlbaugh et al., U.S. Pat. No. 5,082,476, disclose a filterdesign using a depth media comprising a foam substrate with pleatedcomponents combined with the microfiber materials of the invention.Stifelman et al., U.S. Pat. No. 5,104,537, relate to a filter structureuseful for filtering liquid media. Liquid is entrained into the filterhousing, passes through the exterior of the filter into an interiorannular core and then returns to active use in the structure. Suchfilters are highly useful for filtering hydraulic fluids. Engel et al.,U.S. Pat. No. 5,613,992, show a typical diesel engine air intake filterstructure. The structure obtains air from the external aspect of thehousing that may or may not contain entrained moisture. The air passesthrough the filter while the moisture can pass to the bottom of thehousing and can drain from the housing. Gillingham et al., U.S. Pat. No.5,820,646, disclose a Z filter structure that uses a specific pleatedfilter design involving plugged passages that require a fluid stream topass through at least one layer of filter media in a “Z” shaped path toobtain proper filtering performance. The filter media formed into thepleated Z shaped format can contain the fine fiber media of theinvention. Glen et al., U.S. Pat. No. 5,853,442, disclose a bag housestructure having filter elements that can contain the fine fiberstructures of the invention. Berkhoel et al., U.S. Pat. No. 5,954,849,show a dust collector structure useful in processing typically airhaving large dust loads to filter dust from an air stream afterprocessing a workpiece generates a significant dust load in anenvironmental air. Lastly, Gillingham, U.S. Design Patent No. 425,189,discloses a panel filter using the Z filter design.

[0207] The following materials were produced using the followingelectrospin process conditions.

[0208] The following materials were spun using either a rotating emittersystem or a capillary needle system. Both were found to producesubstantially the same fibrous materials.

[0209] Using the device generally a fiber is made. The flow rate was 1.5mil/min per emitter, a target distance of 8 inches, an emitter voltageof 88 kV, a relative humidity of 45%, and for the rotating emitter anrpm of 35.

EXAMPLE 1 Effect of Fiber Size

[0210] Fine fiber samples were prepared from a copolymer of nylon 6, 66,610 nylon copolymer resin (SVP-651) was analyzed for molecular weight bythe end group titration. (J. E. Walz and G. B. Taylor, determination ofthe molecular weight of nylon, Anal. Chem. Vol. 19, Number 7, pp 448450(1947). Number average molecular weight was between 21,500 and 24,800.The composition was estimated by the phase diagram of melt temperatureof three component nylon, nylon 6 about 45%, nylon 66 about 20% andnylon 610 about 25%. (Page 286, Nylon Plastics Handbook, Melvin Kohaned. Hanser Publisher, New York (1995)).Reported physical properties ofSVP 651 resin are: Property ASTM Method Units Typical Value SpecificGravity D-792 —   1.08 Water Absorption D-570 %   2.5 (24 hr immersion)Hardness D-240 Shore D 65  Melting Point DSC ° C.(° F.) 154 (309)Tensile Strength D-638 MPa (kpsi)  50 (7.3) @ Yield Elongation at BreakD-638 % 350  Flexural Modulus D-790 MPa (kpsi) 180 (26) VolumeResistivity D-257 ohm-cm 10¹²

[0211] to produce fiber of 0.23 and 0.45 micron in diameter. Sampleswere soaked in room temperature water, air dried and its efficiency wasmeasured. Bigger fiber takes longer time to degrade and the level ofdegradation was less as can be seen in the plot of FIG. 12. Whilewishing not to be limited by certain theory, it appears that smallerfibers with a higher surface/volume ratio are more susceptible todegradation due to environmental effects. However, bigger fibers do notmake as efficient filter medium.

EXAMPLE 2 Cross-Linking of Nylon Fibers with Phenolic Resin and EpoxyResin

[0212] In order to improve chemical resistance of fibers, chemicalcross-linking of nylon fibers was attempted. Copolyamide (nylon 6, 66,610) described earlier is mixed with phenolic resin, identified asGeorgia Pacific 5137 and spun into fiber. Nylon:Phenolic Resin ratio andits melt temperature of blends are shown here; Composition MeltingTemperature (° F.) Polyamide:Phenolic = 100:0 150 Polyamide:Phenolic =80:20 110 Polyamide:Phenolic = 65:35 94 Polyamide:Phenolic = 50:50 65

[0213] We were able to produce comparable fiber from the blends. The50:50 blend could not be cross-linked via heat as the fibrous structurewas destroyed. Heating 65:35 blend below 90 degree C. for 12 hoursimproves the chemical resistance of the resultant fibers to resistdissolution in alcohol. Blends of polyamide with epoxy resin, such Epon828 from Shell and Epi-Rez 510 can be used.

EXAMPLE 3 Surface Modification Though Fluoro Additive (Scotchgard®)Repellant

[0214] Alcohol miscible Scotchgard® FC430 and 431 from 3M Company wereadded to polyamide before spinning. Add-on amount was 10% of solids.Addition of Scotchgard did not hinder fiber formation. THC bench showsthat Scotchgard-like high molecular weight repellant finish did notimprove water resistance. Scotchgard added samples were heated at 300 F°for 10 minutes as suggested by manufacturer.

EXAMPLE 4 Modification with Coupling Agents

[0215] Polymeric films were cast from polyamides with tinanate couplingagents from Kenrich Petrochemicals, Inc. They include isopropyltriisostearoyl titanate (KR TTS), neopentyl (diallyl) oxytri (dioctyl)phosphato titanate (LICA12), neopentyl (dially) oxy, tri (N-ethylenediamino) ethyl zirconate (NZ44). Cast films were soaked in boilingwater. Control sample without coupling agent loses its strengthimmediately, while coupling agent added samples maintained its form forup to ten minutes. These coupling agents added samples were spun intofiber (0.2 micron fiber).

EXAMPLE 5 Modification with Low Molecular Weight p-tert-butyl PhenolPolymer

[0216] Oligomers of para-tert-butyl phenol, molecular weight range 400to 1100, was purchased from Enzymol International, Columbus, Ohio. Theselow molecular weight polymers are soluble in low alcohols, such asethanol, isopropanol and butanol. These polymers were added toco-polyamide described earlier and electrospun into 0.2 micron fiberswithout adverse consequences. Some polymers and additives hinder theelectrospinning process. Unlike the conventional phenolic resindescribed in Example 2, we have found that this group of polymers doesnot interfere with fiber forming process.

[0217] We have found that this group of additive protects fine fibersfrom wet environment as see in the plot. FIGS. 13-16 show that oligomersprovide a very good protection at 140 F°, 100% humidity and theperformance is not very good at 160 F°. We have added this additivebetween 5% and 15% of polymer used. We have found that they are equallyeffective protecting fibers from exposure to high humidity at 140 F°. Wehave also found out that performance is enhanced when the fibers aresubjected to 150 C° for short period of time.

[0218] The table 1 shows the effect of temperature and time exposure of10% add-on to polyamide fibers. Efficiency Retained (%) After 140 deg.F. Soak: Heating Time Temperature 1 min 3 min 10 min 150° C. 98.9 98.898.5 98.8 98.9 98.8 130° C. 95.4 98.7 99.8 96.7 98.6 99.6 110° C. 82.890.5 91.7 86.2 90.9 85.7

[0219] This was a surprising result. We saw dramatic improvement inwater resistance with this family of additives. In order to understandhow this group of additive works, we have analyzed the fine fiber matwith surface analysis techniques called ESCA. 10% add-on samples shownin Table 1 were analyzed with ESCA at the University of Minnesota withthe results shown in Table 2. TABLE 2 Surface Composition(Polymer:Additive Ratio) Heating Time Temperature 1 min 3 min 10 min150° C. 40:60 40:60 50:50 130° C. 60:40 56:44 62:82 110° C. 63:37 64:3659:41 No Heat 77:23

[0220] Initially, it did not seem to make sense to find surfaceconcentration of additive more than twice of bulk concentration.However, we believe that this can be explained by the molecular weightof the additives. Molecular weight of the additive of about 600 is muchsmaller than that of host fiber forming polymer. As they are smaller insize, they can move along evaporating solvent molecules. Thus, weachieve higher surface concentration of additives. Further treatmentincreases the surface concentration of the protective additive. However,at 10 min exposure, 150 C°, did not increase concentration. This may bean indication that mixing of two components of copolyamide and oligomermolecules is happening as long chain polymer has a time to move around.What this analysis has taught us is that proper selection of posttreatment time and temperature can enhance performance, while too longexposure could have a negative influence.

[0221] We further examined the surface of these additive ladenmicrofibers using techniques called Time of Flight SIMS. This techniqueinvolves bombarding the subject with electrons and observes what iscoming from the surface. The samples without additives show organicnitrogen species are coming off upon bombardment with electron. This isan indication that polyamide species are broken off. It also showspresence of small quantity of impurities, such as sodium and silicone.Samples with additive without heat treatment (23% additive concentrationon surface) show a dominant species of t-butyl fragment, and small butunambiguous peaks observed peaks observed for the polyamides. Alsoobserved are high mass peaks with mass differences of 148 amu,corresponding to t-butyl phenol. For the sample treated at 10 min at 150C° (50% surface additive concentration by ESCA analysis), inspectionshows dominance of t-butyl fragments and trace, if at all, of peaks forpolyamide. It does not show peaks associated with whole t-butyl phenoland its polymers. It also shows a peak associated with C₂H₃O fragments.

[0222] The ToF SIMS analysis shows us that bare polyamide fibers willgive off broken nitrogen fragment from exposed polymer chain andcontaminants on the surface with ion bombardment. Additive without heattreatment shows incomplete coverage, indicating that additives do notcover portions of surface. The t-butyl oligomers are loosely organizedon the surface. When ion beam hits the surface, whole molecules can comeoff along with labile t-butyl fragment. Additive with heat treatmentpromotes complete coverage on the surface. In addition, the moleculesare tightly arranged so that only labile fragments such as t-butyl-, andpossibly CH═CH—OH, are coming off and the whole molecules of t-butylphenol are not coming off. ESCA and ToF SIMS look at different depths ofsurface. ESCA looks at deeper surface up to 100 Angstrom while ToF SIMSonly looks at 10-Angstrom depth. These analyses agree.

EXAMPLE 6 Development of Surface Coated Interpolymer

[0223] Type 8 Nylon was originally developed to prepare soluble andcrosslinkable resin for coating and adhesive application. This type ofpolymer is made by the reaction of polyamide 66 with formaldehyde andalcohol in the presence of acid. (Ref. Cairns, T. L.; Foster, H. D.;Larcher, A. W.; Schneider, A. K.; Schreiber, R. S. J. Am. Chem. Soc.1949, 71, 651). This type of polymer can be electrospun and can becross-linked. However, formation of fiber from this polymer is inferiorto copolyamides and crosslinking can be tricky.

[0224] In order to prepare type 8 nylon, 10-gallon high-pressure reactorwas charged with the following ratio: Nylon 66 (duPont Zytel 101)   10pounds Methanol 15.1 pounds Water  2.0 pounds Formaldehyde 12.0 pounds

[0225] The reactor is then flushed with nitrogen and is heated to atleast 135 C°. under pressure. When the desired temperature was reached,small quantity of acid was added as catalyst. Acidic catalysts includetrifluoroacetic acid, formic acid, toluene sulfonic acid, maleic acid,maleic anhydride, phthalic acid, phthalic anhydride, phosphoric acid,citric acid and mixtures thereof. Nafion® polymer can also be used as acatalyst. After addition of catalyst, reaction proceeds up to 30minutes. Viscous homogeneous polymer solution is formed at this stage.After the specified reaction time, the content of the high pressurevessel is transferred to a bath containing methanol, water and base,like ammonium hydroxide or sodium hydroxide to shortstop the reaction.After the solution is sufficiently quenched, the solution isprecipitated in deionized water. Fluffy granules of polymer are formed.Polymer granules are then centrifuged and vacuum dried. This polymer issoluble in, methanol, ethanol, propanol, butanol and their mixtures withwater of varying proportion. They are also soluble in blends ofdifferent alcohols.

[0226] Thus formed alkoxy alkyl modified type 8 polyamide is dissolvedin ethanol/water mixture. Polymer solution is electrospun in a mannerdescribed in Barris U.S. Pat. No. 4,650,516. Polymer solution viscositytends to increase with time. It is generally known that polymerviscosity has a great influence in determining fiber sizes. Thus, it isdifficult to control the process in commercial scale, continuousproduction. Furthermore, under same conditions, type 8 polyamides do notform microfibers as efficiently as copolyamides. However, when thesolution is prepared with addition of acidic catalyst, such as toluenesulfonic acid, maleic anhydride, trifluoro methane sulfonic acid, citricacid, ascorbic acid and the like, and fiber mats are carefullyheat-treated after fiber formation, the resultant fiber has a very goodchemical resistance. (FIG. 13). Care must be taken during thecrosslinking stage, so that one does not destroy fibrous structure.

[0227] We have found a surprising result when type 8 polyamide (polymerB) is blended with alcohol soluble copolyamides. By replacing 30% byweight of alkoxy alkyl modified polyamide 66 with alcohol solublecopolyamide like SVP 637 or 651 (polymer A), Elvamide 8061, synergisticeffects were found. Fiber formation of the blend is more efficient thaneither of the components alone. Soaking in ethanol and measuringfiltration efficiency shows better than 98% filtration efficiencyretention, THC bench testing showing comparable results with Type 8polyamide alone. This type blend shows that we can obtain advantage ofefficient fiber formation and excellent filtration characteristic ofcopolyamide with advantage of excellent chemical resistance ofcrosslinked type 8 polyamide. Alcohol soak test strongly suggests thatnon-crosslinkable copolyamide has participated in crosslinking tomaintain 98% of filtration efficiency.

[0228] DSC (see FIGS. 17-20) of blends of polymer A and B becomeindistinguishable from that of polymer A alone after they are heated to250 C°. (fully crosslinked) with no distinct melt temperature. Thisstrongly suggests that blends of polymer A and B are a fully integratedpolymer by polymer B crosslinking with polymer A. This is a completelynew class of polyamide.

[0229] Similarly, melt-blend poly (ethylene terephthalate) withpoly(butylene terephthalate) can have similar properties. During themelt processing at temperatures higher than melt temperature of eithercomponent, ester group exchange occurs and inter polymer of PET and PBTformed. Furthermore, our crosslinking temperature is lower than eitherof single component. One would not have expected that such groupexchange occur at this low temperature. Therefore, we believe that wefound a new family of polyamide through solution blending of Type A andType B polyamide and crosslinking at temperature lower than the meltingpoint of either component.

[0230] When we added 10% by weight of t-butyl phenol oligomer (Additive7) and heat treated at temperature necessary for crosslinkingtemperature, we have found even better results. We theorized thathydroxyl functional group of t-butyl phenol oligomers would participatein reaction with functional group of type 8 nylons. What we have foundis this component system provides good fiber formation, improvedresistance to high temperature and high humidity and hydrophobicity tothe surface of fine fiber layers.

[0231] We have prepared samples of mixture of Polymer A and Polymer B(Sample 6A) and another sample of mixture of Polymer A, Polymer B andAdditive & (Sample 6B). We then formed fiber by electrospinning process,exposed the fiber mat at 300° F. for 10 minutes and evaluated thesurface composition by ESCA surface analysis.

[0232] Table shows ESCA analysis of Samples 6A and 6B. Composition (%)Sample 6A Sample 6B Polymer A 30 30 Polymer B 70 70 Additive 7  0 10Surface Composition W/O Heat W/Heat W/O Heat W/Heat Polymer A&B (%) 100100 68.9 43.0 Additive 7  0  0 31.1 57.0

[0233] ESCA provides information regarding surface composition, exceptthe concentration of hydrogen. It provides information on carbon,nitrogen and oxygen. Since the Additive 7 does not contain nitrogen, wecan estimate the ratio of nitrogen containing polyamides and additivethat does not contain nitrogen by comparing concentration of nitrogen.Additional qualitative information is available by examining O 1sspectrum of binding energy between 535 and 527 eV. C=O bond has abinding energy at around 531 eV and C—O bond has a binding energy at 533eV. By comparing peak heights at these two peaks, one can estimaterelative concentration of polyamide with predominant C═O and additivewith solely C—O groups. Polymer B has C—O linkage due to modificationand upon crosslinking the concentration of C—O will decrease. ESCAconfirms such reaction had indeed occurred, showing relative decrease ofC—O linkage. (FIG. 4 for non heat treated mixture fiber of Polymer A andPolymer B, FIG. 5 for heat treated mixture fiber of Polymer A andPolymer B). When Additive 7 molecules are present on the surface, onecan expect more of C—O linkage. This is indeed the case as can be seenin FIGS. 6 and 7. (FIG. 6 for as-spun mixture fibers of Polymer A,Polymer B and Additive 7. FIG. 7 for heat treated mixture fibers ofPolymer A, Polymer B and Additive 7). FIG. 6 shows that theconcentration of C—O linkage increases for Example 7. The finding isconsistent with the surface concentration based on XPS multiplexspectrum of FIGS. 8 through 11.

[0234] The t-butyl oligomer molecules migrate toward the surface of thefine fibers and form hydrophobic coating of about 50 Å. Type 8 nylon hasfunctional groups such as —CH₂OH and —CH₂OCH₃, which we expected toreact with —OH group of t-butyl phenol. Thus, we expected to see lessoligomer molecules on the surface of the fibers. We have found that ourhypothesis was not correct and we found the surface of the interpolymerhas a thin coating.

[0235] Samples 6A, 6B and a repeat of sample described in Section 5 havebeen exposed THC bench at 160° F. at 100% RH. In previous section, thesamples were exposed to 140° F. and 100% RH. Under these conditions,t-butyl phenol protected terpolymer copolyamide from degradation.However, if the temperature is raised to 160° F. and 100% RH, then thet-butyl phenol oligomer is not as good in protecting the underlyingterpolymer copolyamide fibers. We have compared samples at 160° F. and100% RH. TABLE Retained Fine Fiber Efficiency after Exposure to 160° F.and 100% RH Sample After 1 Hr. After 2 Hrs. After 3 Hrs. Sample 6A 82.682.6 85.9 Sample 6B 82.4 88.4 91.6 Sample 5 10.1

[0236] The table shows that Sample 6B helps protect exposure to hightemperature and high humidity.

[0237] More striking difference shows when we exposed to droplets ofwater on a fiber mat. When we place a drop of DI water in the surface ofSample 6A, the water drops immediately spread across the fiber mat andthey wet the substrate paper as well. On the other hand, when we place adrop of water on the surface of Sample 6B, the water drop forms a beadand did not spread on the surface of the mat. We have modified thesurface of Sample 16 to be hydrophobic by addition of oligomers ofp-t-butyl phenol. This type of product can be used as a water misteliminator, as water drops will not go through the fine fiber surfacelayer of Sample 6B.

[0238] Samples 6A, 6B and a repeat sample of Section 5 were placed in anoven where the temperature was set at 310° F. Table shows that bothSamples 6A and 6B remain intact while Sample of Section 5 was severelydamaged. TABLE Retained Fine Fiber Efficiency after Exposure to 310° F.Sample After 6 Hrs. After 77 Hrs. Sample 6A 100% 100% Sample 6B 100%100% Sample 5  34%  33%

[0239] While addition of oligomer to Polymer A alone improved the hightemperature resistance of fine fiber layer, the addition of Additive 7has a neutral effect on the high temperature exposure.

[0240] We have clearly shown that the mixture of terpolymer copolyamide,alkoxy alkyl modified nylon 66 and oligomers of t-butyl phenol providesa superior products in helping fine fibers under severe environment withimproved productivity in manufacturing over either mixture of terpolymercopolyamide and t-butyl phenol oligomer or the mixture of terpolymercopolyamide and alkoxy alkyl modified nylon 66. These two componentsmixture are also improvement over single component system.

EXAMPLE 7 Compatible Blend of Polyamides and Bisphenol A polymers

[0241] A new family of polymers can be prepared by oxidative coupling ofphenolic ring (Pecora, A; Cyrus, W. U.S. Pat. No. 4,900,671(1990) andPecora, A; Cyrus, W.; Johnson, M. U.S. Pat. No. 5,153,298(1992)). Ofparticular interest is polymer made of Bisphenol A sold by Enzymol Corp.Soybean Peroxidase catalyzed oxidation of Bisphenol A can start fromeither side of two —OH groups in Bisphenol A. Unlike Bisphenol A basedpolycarbonate, which is linear, this type of Bisphenol A polymer formshyperbranched polymers. Because of hyperbranched nature of this polymer,they can lower viscosity of polymer blend.

[0242] We have found that this type of Bisphenol A polymer can besolution blended with polyamides. Reported Hansen's solubility parameterfor nylon is 18.6. (Page 317, Handbook of Solubility Parameters andother cohesion parameters, A. Barton ed., CRC Press, Boca Raton Fla.,1985) If one calculates solubility parameter (page 61, Handbook ofSolubility Parameters), then the calculated solubility parameter is28.0. Due to the differences in solubility parameter, one would notexpect that they would be miscible with each other. However, we foundthat they are quite miscible and provide unexpected properties.

[0243] 50:50 blend of Bisphenol A resin of M.W. 3,000 and copolyamidewas made in ethanol solution. Total concentration in solution was 10%.Copolyamide alone would have resulted in 0.2 micron fiber diameter.Blend resulted in lofty layer of fibers around 1 micron. Bisphenol A of7,000 M.W. is not stable with copolyamide and tends to precipitate.

[0244] DSC of 50:50 blend shows lack of melting temperature. Copolyamidehas melting temperature around 150 degree C. and Bisphenol A resin is aglassy polymer with Tg of about 100. The blend shows lack of distinctmelting. When the fiber mat is exposed to 100 degree C., the fiber matdisappears. This blend would make an excellent filter media where upperuse temperature is not very high, but low-pressure drop is required.This polymer system could not be crosslinked with a reasonable manner.

EXAMPLE 8 Dual Roles of Bisphenol A Polymer As Solvent and Solid inBlend

[0245] A surprising feature of Bisphenol A polymer blend is that insolution form Bisphenol A polymer acts like a solvent and in solid formthe polymer acts as a solid. We find dual role of Bisphenol A polymertruly unique.

[0246] The following formulation is made: Alkoxy alkyl modified PA 66:Polymer B 180 g Bisphenol A Resin (3,000 MW): Polymer C 108 g Ethanol190 Grade 827 g Acetone 218 g DI water 167 g Catalyst  9.3 g

[0247] The viscosity of this blend was 32.6 centipoise by Brookfieldviscometer. Total polymer concentration was be 19.2%. Viscosity ofPolymer B at 19.2% is over 200 centipoise. Viscosity of 12% polymer Balone in similar solvent is around 60 centipoise. This is a clearexample that Bisphenol A resin acts like a solvent because the viscosityof the total solution was lower than expected. Resultant fiber diameterwas 0.157 micron. If polymer B alone participated in fiber formation,the expected fiber size would be less than 0.1 micron. In other words,Polymer C participated in fiber formation. We do not know of any othercase of such dramatic dual role of a component. After soaking the samplein ethanol, the filtration efficiency and fiber size was measured. Afteralcohol soak, 85.6% of filtration efficiency was retained and the fibersize was unchanged. This indicates that Polymer C has participated incrosslinking acting like a polymer solid.

[0248] Another polymer solution was prepared in the following manner:Alkoxy alkyl Modified PA66: Polymer B 225 g Bisphenol A Resin (3,000MW): Polymer C 135 g Ethanol 190 Grade 778 g Acetone 205 g DI Water 157g Catalyst 11.6 g 

[0249] Viscosity of this blend was 90.2 centipoise. This is a very lowviscosity value for 24% solid. Again, this is an indication Polymer Cacts like a solvent in the solution. However, when they are electrospuninto fiber, the fiber diameter is 0.438 micron. 15% solution of PolymerB alone would have produced around 0.2-micron fibers. In final state,Polymer C contributes to enlarging fiber sizes. Again, this exampleillustrates that this type of branched polymer acts as a solvent insolution and acts as a solid in final state. After soaking in ethanolsolution, 77.9% of filtration efficiency was retained and fiber size wasunchanged.

EXAMPLE 9 Development of Crosslinked Polyamides/Bisphenol A PolymerBlends

[0250] Three different samples were prepared by combining resins,alcohols and water, stirring 2 hours at 60 degree C. The solution iscooled to room temperature and catalyst was added to solution and themixture was stirred another 15 minutes. Afterward, viscosity of solutionwas measured and spun into fibers.

The following table shows these examples:

[0251] Recipe (g) Sample 9A Sample 9B Sample 9C Polymer B 8.4 12.6 14.7Polymer A 3.6 5.4 6.3 Polymer C 7.2 10.8 12.6 Ethanol 190 Grade 89.382.7 79.5 Isopropanol 23.5 21.8 21.0 DI Water 18.0 16.7 15.9 Catalyst.45 0.58 0.79 Viscosity (cP) 22.5 73.5 134.2 Fiber Size (micron) 0.140.258 0.496

[0252] We have found out that this blend generates fibers efficiently,producing about 50% more mass of fiber compared to Polymer A recipe. Inaddition, resultant polymeric microfibers produce a more chemicallyresistant fiber. After alcohol soak, a filter made from these fibersmaintained more than 90% filtration efficiency and unchanged fiberdiameter even though inherently crosslinkable polymer is only 44% of thesolid composition. This three-polymer composition of co-polyamide,alkoxy alkyl modified Nylon 66 and Bisphenol A creates excellent fiberforming, chemically resistant material.

EXAMPLE 10 Alkoxy Alkyl Modified Co-Polymer of Nylon 66 and Nylon 46

[0253] In a 10-gallon high-pressure reactor, the following reactionswere made, and resultant polymers were analyzed. After reactiontemperature was reached, catalyst were added and reacted for 15 minutes.Afterward, the polymer solution was quenched, precipitated, washed anddried. Reactor Charge (LB) Run 10A Run 10B Run 10C Run 10D Run 10E Nylon4,6 (duPont Zytel 101) 10 5 5 5 5 Nylon 6,6 (DSM Stanyl 300) 0 5 5 5 5Formaldehyde 8 10 8 10 8 DI Water 0.2 0.2 2 0.2 2 Methanol 22 20 20 2020 Reaction Temp (° C.) 140 140 140 150 150 Tg (° C.) 56.7 38.8 37.738.5 31.8 Tm (° C.) 241.1 162.3 184.9 175.4 189.5 Level of SubstitutionAlkoxy (wt. %) 11.9 11.7 7.1 11.1 8.4 Methylol (wt %) 0.14 0.13 0.140.26 0.24

[0254] DSC of the polymer made with Nylon 46 and Nylon 66 shows broadsingle melt temperature, which are lower than the melting temperature ofmodified Nylon 46 (241 C°) or modified Nylon 66 (210 C°). This is anindication that during the reaction, both components are randomlydistributed along the polymer chain. Thus, we believe that we haveachieved random copolymer of Nylon 46 and Nylon 66 with alkoxy alkylmodification. These polymers are soluble in alcohols and mixtures ofalcohol and water. Property ASTM Nylon 6.6 Nylon 4.6 T_(m) 265° C. 295°C. Tensile Strength D638 13.700 8.500 Elongation at Break D638 15-80 60Tensile Yield Strength D638   8000-12,000 Flexural Strength D790 17,800011,500 Tensile Modulus × 10³ psi D638 230-550 250 Izod Impact ft-lb/inof notch D256A 0.55-1.0  17 Deflection Temp Under D648 158 194 FlexuralLoad 264 psi

[0255] Both are highly crystalline and are not soluble in commonalcohols.

[0256] Source: Modern Plastics Encyclopedia 1998

EXAMPLE 11 Development of Interpolymer of Coplyamides and AlkoxyalkylModified Nylon 46/66 Copolymer and Formation of Electrospun Fibers

[0257] Runs 10B and 10D samples were made into fibers by methodsdescribed in above. Alkoxy alkyl modified Nylon 46/66 (Polymer D) alonewere successfully electrospun. Blending Polymer D with Polymer A bringsadditional benefits of more efficient fiber formation and ability tomake bigger fibers without sacrificing the crosslinkability of Polymer Das can be seen in the following table: Polymer 10B Polymer 10D w/30%w/30% Alone Polymer A Alone Polymer A Fiber Size(micron) 0.183 0.4640.19 0.3 Fiber Mass Ratio 1 3 1 2 Filtration Effi. Retention(%) 87 90 9290

[0258] Fiber Mass Ratio is calculated by (total length of fiber timescross sectional area). Filtration Efficiency Retention is measuredsoaking filter sample in ethanol. Fiber size was unchanged by alcoholsoak.

EXAMPLE 12 Crosslinked, Electrospun PVA

[0259] PVA powders were purchased from Aldrich Chemicals. They weredissolved either in water or 50/50 mixture of methanol and water. Theywere mixed with crosslinking agent and toluene sulfonic acid catalystbefore electrospinning. The resulting fiber mat was crosslinked in anoven at 150° C. for 10 minutes before exposing to THC bench. PVA Sample12A Sample 12B Sample 12C Sample 12D Hydrolysis    98-99    87-89   87-89    87-89 M.W. 31,500-50,000 31,500-50,000 31,500-50,00031,500-50,000 PVA 10 10 10 10 Conc. (%) Solvent Water Mixture Mixture(c) Mixture (d) Other Polymer None None Acrylic Acid Cymel 385 OtherPolymer/  0  0 30 30 PVA (%) % Fiber  0 (a)  0 (a,b) 95 (b) 20 (b)Retained THC, 1 hr. % Fiber 90 (a) Retained THC, 3 hr.

EXAMPLE 13

[0260] A conventional cellulose air filter media was used as thesubstrate. This substrate had a basis weight of 67 pounds per 3000square feet, a Frazier permeability of 16 feet per minute at 0.5 inchesof water pressure drop, a thickness of 0.012 inches, and a LEFSefficiency of 41.6%. A fine fiber layer of Example 1 was added to thesurface using the process described with a nominal fiber diameter of 0.2microns. The resulting composite had a LEFS efficiency of 63.7%. Afterexposure to 140F air at 100% relative humidity for 1 hour the substrateonly sample was allowed to cool and dry, it then had a LEFS efficiencyof 36.5%. After exposure to 140F air at 100% relative humidity for 1hour the composite sample was allowed to cool and dry, it then had aLEFS efficiency of 39.7%. Using the mathematical formulas described, thefine fiber layer efficiency retained after 1 hour of exposure was 13%,the number of effective fine fibers retained was 11%.

EXAMPLE 14

[0261] A conventional cellulose air filter media was used as thesubstrate. This substrate had a basis weight of 67 pounds per 3000square feet, a Frazier permeability of 16 feet per minute at 0.5 inchesof water pressure drop, a thickness of 0.012 inches, and a LEFSefficiency of 41.6%. A fine fiber layer of Example 5 was added to thesurface using the process described with a nominal fiber diameter of 0.2microns. The resulting composite had a LEFS efficiency of 96.0%. Afterexposure to 160F air at 100% relative humidity for 3 hours the substrateonly sample was allowed to cool and dry, it then had a LEFS efficiencyof 35.3%. After exposure to 160F air at 100% relative humidity for 3hours the composite sample was allowed to cool and dry, it then had aLEFS efficiency of 68.0%. Using the mathematical formulas described, thefine fiber layer efficiency retained after 3 hours of exposure was 58%,the number of effective fine fibers retained was 29%.

EXAMPLE 15

[0262] A conventional cellulose air filter media was used as thesubstrate. This substrate had a basis weight of 67 pounds per 3000square feet, a Frazier permeability of 16 feet per minute at 0.5 inchesof water pressure drop, a thickness of 0.012 inches, and a LEFSefficiency of 41.6%. A fine fiber layer of a blend of Polymer A andPolymer B as described in Example 6 was added to the surface using theprocess described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 92.9%. After exposure to160F air at 100% relative humidity for 3 hours the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 35.3%.After exposure to 160F air at 100% relative humidity for 3 hours thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 86.0%. Using the mathematical formulas described, the finefiber layer efficiency retained after 3 hours of exposure was 96%, thenumber of effective fine fibers retained was 89%.

EXAMPLE 16

[0263] A conventional cellulose air filter media was used as thesubstrate. This substrate had a basis weight of 67 pounds per 3000square feet, a Frazier permeability of 16 feet per minute at 0.5 inchesof water pressure drop, a thickness of 0.012 inches, and a LEFSefficiency of 41.6%. A fine fiber layer of Polymer A, Polymer B, t-butylphenol oligomer as described in Example 6 was added to the surface usingthe process described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 90.4%. After exposure to160F air at 100% relative humidity for 3 hours the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 35.3%.After exposure to 160F air at 100% relative humidity for 3 hours thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 87.3%. Using the mathematical formulas described, the finefiber layer efficiency retained after 3 hours of exposure was 97%, thenumber of effective fine fibers retained was 92%.

EXAMPLE 17

[0264] A conventional cellulose air filter media was used as thesubstrate. This substrate had a basis weight of 67 pounds per 3000square feet, a Frazier permeability of 16 feet per minute at 0.5 inchesof water pressure drop, a thickness of 0.012 inches, and a LEFSefficiency of 41.6%. A fine fiber layer of crosslinked PVA withpolyacrylic acid of Example 12 was added to the surface using theprocess described with a nominal fiber diameter of 0.2 microns. Theresulting composite had a LEFS efficiency of 92.9%. After exposure to160F air at 100% relative humidity for 2 hours the substrate only samplewas allowed to cool and dry, it then had a LEFS efficiency of 35.3%.After exposure to 160F air at 100% relative humidity for 2 hours thecomposite sample was allowed to cool and dry, it then had a LEFSefficiency of 83.1%. Using the mathematical formulas described, the finefiber layer efficiency retained after 2 hours of exposure was 89%, thenumber of effective fine fibers retained was 76%.

EXAMPLE 18

[0265] The following filter medias have been made with the methodsdescribed in Example 1-17. Filter Media Examples Substrate permSubstrate Basis wt Substrate Substrate Composite Substrate (Frazier)(lbs/3000 sq ft) Thickness (in) Eff (LEFS) Eff (LEFS Single fine fiberlayer on (+/−10% (+/−10%) (+/−25%) (+/−5%) (+/−5%) single substrate(flow either direction through media Cellulose air filter media 58 670.012 11% 50% Cellulose air filter media 16 67 0.012 43% 58% Celluloseair filter media 58 67 0.012 11% 65% Cellulose air filter media 16 670.012 43% 70% Cellulose air filter media 22 52 0.010 17% 70% Celluloseair filter media 16 67 0.012 43% 72% Cellulose/synthetic blend 14 700.012 30% 70% with moisture resistant resin Flame retardant cellulose 1777 0.012 31% 58% air filter media Flame retardant cellulose 17 77 0.01231% 72% air filter media Flame retardant synthetic 27 83 0.012 77% airfilter media Spunbond Remay 1200 15 0.007 5% 55% (polyester)Synthetic/cellulose air 260 76 0.015 6% 17% filter media Synthetic/glassair filter 31 70 0.012 55% 77% media Synthetic/glass air filter 31 700.012 50% 90% media Single fine fiber layer on substrate. Two layers ofcomposite are then laminated together (fine fiber layers on the inside-substrates on the outside) Synthetic (Lutrador- 300 25 0.008 3% 65%polyester) Synthetic (Lutrador- 0.016 90% polyester)

[0266] Media has been used flat, corrugated, pleated, corrugated andpleated, in flatsheets, pleated flat panels, pleated round filters, andZee filters.

Test Methods

[0267] Hot Water Soak Test

[0268] Using filtration efficiency as the measure of the number of finefibers effectively and functionally retained in structure has a numberof advantages over other possible methods such as SEM evaluation.

[0269] the filtration measure evaluates several square inches of mediayielding a better average than the tiny area seen in SEMphotomicrographs (usually less than 0.0001 square inch

[0270] the filtration measurement quantifies the number of fibersremaining functional in the structure. Those fibers that remain, but areclumped together or otherwise existing in an altered structure are onlyincluded by their measured effectiveness and functionality.

[0271] Nevertheless, in fibrous structures where the filtrationefficiency is not easily measured, other methods can be used to measurethe percent of fiber remaining and evaluated against the 50% retentioncriteria.

[0272] Description: This test is an accelerated indicator of filtermedia moisture resistance. The test uses the LEFS test bench to measurefilter media performance changes upon immersion in water. Watertemperature is a critical parameter and is chosen based on thesurvivability history of the media under investigation, the desire tominimize the test time and the ability of the test to discrite betweenmedia types. Typicdl water temperatures re 70° F., 140° F. or 160° F.

[0273] Procedure:

[0274] A 4″ diameter sample is cut from the media. Particle captureefficiency of the test specimen is calculated using 0.8 μm latex spheresas a test challenge contaminant in the LEFS (for a description of theLEFS test, see ASTM Standard F1215-89) bench operating at 20 FPM. Thesample is then submerged in (typically 140° F.) distilled water for 5minutes. The sample is then placed on a drying rack and dried at roomtemperature (typically overnight). Once it is dry the sample is thenretested for efficiency on the LEFS bench using the same conditions forthe initial calculation.

[0275] The previous steps are repeated for the fine fiber supportingsubstrate without fine fiber.

[0276] From the above information one can calculate the efficiencycomponent due only to the fine fiber and the resulting loss inefficiency due to water damage. Once the loss in efficiency due to thefine fiber is determined one can calculate the amount of efficiencyretained.

[0277] Calculations:

[0278] Fine fiber layer efficiency: E_(i)=Initial Composite Efficiency;

[0279] E_(s)=Initial Substrate Efficiency;

[0280] F_(e)=Fine Fiber Layer

[0281] F_(e)=1−EXP(Ln(1−E_(i))−Ln(1−E_(x)))

[0282] Fine fiber layer efficiency retained: F_(i)=Initial fine fiberlayer efficiency;

[0283] F_(x)=Post soak fine fiber layer efficiency;

[0284] F_(r)=Fine fiber retained

F _(r) =F _(x) /F _(i)

[0285] The percentage of the fine fibers retained with effectivefunctionality can also be calculated by:

%=log(1−F _(x))/log(1−F _(i))

[0286] Pass/Fail Criteria: >50% efficiency retention

[0287] In most industrial pulse cleaning filter applications the filterwould perform adequately if at least 50% of the fine fiber efficiency isretained.

[0288] THC Bench (Temperature, Humidity

[0289] Description: The purpose of this bench is to evaluate fine fibermedia resistance to the affects of elevated temperature and highhumidity under dynamic flow conditions. The test is intended to simulateextreme operating conditions of either an industrial filtrationapplication, gas turbine inlet application, or heavy duty engine airintake environments. Samples are taken out, dried and LEFS tested atintervals. This system is mostly used to simulate hot humid conditionsbut can also be used to simulate hot/cold dry situations. Temperature−31 to 390° F. Humidity 0 to 100% RH (Max temp for 100% RH is 160° F.and max continuous duration at this condition is 16 hours) Flow Rate 1to 35 FPM Procedure: A 4″ diameter sample is cut from the media.

[0290] Particle capture efficiency of the test specimen is calculatedusing 0.8 μm latex spheres as a test challenge contaminant in the LEFSbench operating at 20 FPM.

[0291] The sample is then inserted into the THC media chuck.

[0292] Test times can be from minutes to days depending on testingconditions.

[0293] The sample is then placed on a drying rack and dried at roomtemperature (typically overnight). Once it is dry the sample is thenretested for efficiency on the LEFS bench using the same conditions forthe initial calculation.

[0294] The previous steps are repeated for the fine fiber supportingsubstrate without fine fiber. From the above information one cancalculate the efficiency component due only to the fine fiber and theresulting loss in efficiency due to alcohol damage.

[0295] Once the loss in efficiency due to the fine fiber is determinedone can calculate the amount of efficiency retained.

[0296] Pass/Fail Criteria: >50% efficiency retention

[0297] In most industrial pulse cleaning filter applications the filterwould perform adequately if at least 50% of the fine fiber efficiency isretained.

[0298] Alcohol (Ethanol) Soak Test

[0299] Description: The test uses the LEFS test bench to measure filtermedia performance changes upon immersion in room temperature ethanol.

[0300] Procedure:

[0301] A 4″ diameter sample is cut from the media. Particle captureefficiency of the test specimen is calculated using 0.8 μm latex spheresas a test challenge contaminant in the LEFS bench operating at 20 FPM.The sample is then submerged in alcohol for 1 minute.

[0302] The sample is then placed on a drying rack and dried at roomtemperature (typically overnight). Once it is dry the sample is thenretested for efficiency on the LEFS bench using the same conditions forthe initial calculation. The previous steps are repeated for the finefiber supporting substrate without fine fiber. From the aboveinformation one can calculate the efficiency component due only to thefine fiber and the resulting loss in efficiency due to alcohol damage.Once the loss in efficiency due to the fine fiber is determined one cancalculate the amount of efficiency retained.

[0303] Pass/Fail Criteria: >50% efficiency retention.

[0304] The above specification, examples and data provide an explanationof the invention. However, many variations and embodiments can be madeto the disclosed invention. The invention is embodied in the claimsherein after appended.

What is claimed is:
 1. A filter element arrangement comprising: (a) amedia pack having a substrate comprising first and second opposite flowfaces and a plurality of flutes wherein in said media pack; (i) each ofsaid flutes have a first end portion adjacent to said first flow faceand a second end portion adjacent to said second flow face; (ii)selected ones of said flutes being open at said first end portion andclosed at said second end portion; and selected ones of said flutesbeing closed at said first end portion and open at said second endportion (iii) said substrate at least partially covered by a layercomprising fine fiber comprising a fiber with a diameter of about 0.01to 0.5 microns such that the fiber, when tested under conditions ofexposure for a test period of 16 hours to test conditions of 140° F. airat a relative humidity of 100%, retains greater than 30% of the fiberunchanged for filtration purposes
 2. The element of claim 1 wherein thepolymer comprises an addition polymer.
 3. The element of claim 2 whereinthe addition polymer comprises a polyvinyl halide polymer, apolyvinylidene halide polymer or mixtures thereof.
 4. The element ofclaim 3 wherein the polyvinylidene halide comprises polyvinylidenechloride.
 5. The element of claim 3 wherein the polyvinylidene halidecomprises polyvinylidene fluoride.
 6. The element of claim 2 wherein theaddition polymer comprises a polyvinylalcohol.
 7. The element of claim 2wherein the addition polymer comprises a copolymer comprisingvinylalcohol.
 8. The element of claim 6 wherein the polyvinylalcohol iscrosslinked with about 1 to 40 wt. % of a crosslinking agent.
 9. Theelement of claim 7 wherein the polymer is crosslinked with about 1 to 40wt. % of a crosslinking agent.
 10. The element of claim 8 wherein thecrosslinked polyvinylalcohol is crosslinked using a polyacrylic acidhaving a molecular weight of about 1000 to
 3000. 11. The element ofclaim 8 wherein the crosslinked polyvinylalcohol is crosslinked using amelamine-formaldehyde resin having a molecular weight of about 1000 to3000.
 12. The element of claim 1 comprising a condensation polymer 13.The element of claim 10 comprising a nylon polymer
 14. The element ofclaim 13 wherein the nylon comprises a nylon other than a copolymerformed from a cyclic lactam and a C₆₋₁₀ diamine monomer or a C₆₋₁₀diacid monomer
 15. The element of claim 12 also comprising a resinousadditive comprising an oligomer having a molecular weight of about 500to 3000 and an aromatic character wherein the additive miscible in thecondensation polymer.
 16. The element of claim 12 wherein thecondensation polymer comprises a polyalkylene terephthalate.
 17. Theelement of claim 15 wherein the condensation polymer comprises apolyalkylene naphthalate.
 18. The element of claim 16 wherein thecondensation polymer comprises a polyethylene terephthalate.
 19. Theelement of claim 13 wherein the condensation polymer comprises a nylonpolymer comprising a homopolymer having repeating units derived from acyclic lactam.
 20. The element of claim 13 wherein the nylon copolymeris combined with a second nylon polymer, the second nylon polymerdiffering in molecular weight or monomer composition.
 21. The element ofclaim 20 wherein the nylon copolymer is combined with a second nylonpolymer, the second nylon polymer comprising an alkoxy alkyl modifiedpolyamide.
 22. The element of claim 20 wherein the second nylon polymercomprises a nylon copolymer.
 23. The element of claim 20 wherein thepolymers are treated to form a single polymeric composition as measuredby a differential scanning calorimeter showing a single-phase material.24. The element of claim 23 wherein the copolymer and the second polymerare heat-treated.
 25. The element of claim 24 wherein the copolymer andthe second polymer are heat-treated to a temperature less than the lowermelting point of the polymers.
 26. The element of claim 15 wherein theadditive comprises an oligomer comprising a phenol compound.
 27. Theelement of claim 26 wherein the additive comprises an oligomercomprising tertiary butyl phenol.
 28. The element of claim 24 whereinthe additive comprises an oligomer comprising:


29. The element of claim 26 wherein the resin comprises an oligomercomprising bis-phenol A.
 30. The element of claim 29 wherein theadditive comprises an oligomer comprising:


31. The element of claim 15 wherein the resin comprises an oligomercomprising dihydroxy biphenyl.
 32. The element of claim 31 wherein theadditive comprises an oligomer comprising:


33. The element of claim 15 wherein the additive comprises a blend ofthe resinous additive and a fluoropolymer.
 34. The element of claim 15wherein the additive comprises a fluorocarbon surfactant.
 35. Theelement of claim 15 wherein the additive comprises a nonionicsurfactant.
 36. The element of claim 12 wherein the condensation polymercomprises a polyurethane polymer.
 37. The element of claim 12 whereinthe condensation polymer comprises a blend of a polyurethane polymer anda polyamide polymer.
 38. The element of claim 13 wherein the nyloncomprises a nylon homopolymer, a nylon copolymer or mixtures thereof.39. The element of claim 12 wherein the condensation polymer comprisesan aromatic polyamide.
 40. The element of claim 12 wherein thecondensation polymer comprises a reaction product of a diamine monomerand poly(m-phenylene isophthalamide).
 41. The element of claim 39wherein the polyamide comprises a reaction product of a diamine and apoly(p-phenylene terephthalamide).
 42. The element of claim 12 whereinthe condensation polymer comprises a polybenzimidazole.
 43. The elementof claim 12 wherein the condensation polymer comprises a polyarylate.44. The element of claim 43 wherein the polyarylate polymer comprises acondensation polymerization reaction product between bis-phenol-A andmixed phthalic acids.
 45. A filter element arrangement according toclaim 1 further including: (a) a sealing system including a flameconstruction and a seal member; (i) said frame arrangement including anextension projecting axially from one of said first and second flowfaces; (A) said extension comprises a hoop construction having an outerradial surface; (ii) said seal member being supported by said extensionof said frame arrangement; (A) said seal member comprising polyurethanefoam having an as molded density of 14-22 lbs/ft³; (B) said seal memberbeing oriented against at least said outer radial surface.
 46. A filterelement arrangement according to claim 45 wherein: (a) said media packand said frame construction have a circular cross-section.
 47. A filterelement arrangement according to claim 45 wherein: (a) said media packand said flame construction have a race track shaped cross-section; and(b) said flame construction includes radially supporting cross braces.48. A filter element arrangement according to claim 45 furtherincluding: (a) a panel structure; said media pack being mounted withinsaid panel structure.
 49. A filter element arrangement according toclaim 45 further including: (a) a handle projecting from the first faceof the media pack; said handle being sized to accommodate a human hand.50. A filter element arrangement according to claim 45 furtherincluding: (a) a sleeve member secured to and circumscribing said mediapack; (i) said sleeve member being oriented relative said media pack toextend at least 30% of said axial length of said media pack; and (b) aseal member pressure flange at least partially circumscribing said mediapack. (i) said seal member pressure flange extending radially from saidsleeve member and fully circumscribing said sleeve member.
 51. A methodfor filtering air, the method comprising: (a) directing the air througha media pack at a rate of 5 to 10,000 cfm, the pack comprising asubstrate having first and second opposite flow faces, the substratecomprising a plurality of flutes wherein in said media pack; (i) saidflutes have a first end portion adjacent to the first flow face and asecond end portion adjacent to the second flow face; (ii) selected onesof the flutes being open at the first end portion and closed at thesecond end portion; and selected ones of the flutes being closed at thefirst end portion and open at the second end portion; (iii) the mediacomposite including a substrate at least partially covered by a layercomprising fine fiber comprising a fiber with a diameter of about 0.01to 0.5 microns such that the fiber, when tested under conditions ofexposure for a period of 16 hours to test conditions of 140° F. air at arelative humidity of 100%, retains greater than 30% of the fiberunchanged for filtration purposes.
 52. A method according to claim 51wherein the method comprises a step of directing a pulse of air throughthe media pack to remove particulate collected in the pack.
 53. A methodaccording to claim 52 wherein the pulse is directed in a directionopposite to the flow direction of the air in normal operation.
 54. Amethod according to claim 53 wherein the pulse removes greater than 50%of the particulate in the pack.
 55. A method according to claim 45wherein: (a) the step of directing the air through a media pack includesdirecting the air into an air intake conduit of an engine rated at anengine intake air flow of about 50 to 500 cfm.
 56. A method according toclaim 49 wherein: (a) the step of directing the air through a media packincludes directing the air through a filter element including the mediapack and a sealing system; the sealing system comprising a framearrangement and a seal member; (i) the frame arrangement including anextension projecting axially from one of the first and second flowfaces; (ii) the seal member being supported by the extension of theframe arrangement; and (iii) the seal member forming a radial sealbetween and against the extension and a duct in the engine air intake.57. A method according to claim 45 wherein: (a) the step of directingthe air through a media pack includes directing the air into an airintake conduit of a gas turbine system.
 58. A method according to claim53 wherein: (a) the step of directing the air into an air intake conduitof a gas turbine system includes directing the air into the air intakeconduit of the gas turbine system including: (i) a tube sheet having atleast a single through hole; (ii) a sleeve member removably andreplaceably mounted through the hole; the media pack being held by thesleeve member; (iii) a flange at least partially circumscribing thesleeve member; and (iv) a seal member pressed between and against theflange and the tube sheet to form a seal therebetween.
 59. A methodaccording to claim 51 wherein: (a) the step of directing the air througha media pack includes directing the air into an air intake of a fuelcell system including a filter assembly and a downstream fuel cell. 60.A method according to claim 59 wherein: (a) the step of directing theair through a media pack includes directing the air into the air intakeof the fuel cell system including the filter assembly upstream of thefuel cell, the filter assembly including: (i) a housing having an inletand an outlet, the inlet receiving dirty atmospheric air to the filterassembly, and the outlet receiving clean air from the filter assembly;(A) the media pack being operably installed in the housing; (ii) a soundsuppression element within the housing; the sound suppression elementconstruction and arranged to attenuate at least 6 dB; and the fuel cellhaving an air intake port; the filter assembly constructed and arrangedto provide clean air from the outlet of the filter assembly to theintake port of the fuel cell.